What is the purpose of creating a new wallet for, why not use just 1?

[RedhatCAT]

For further clarification

-snip-
"Bitcoin Address": A string of letters and numbers typically starting with a 1 or a 3 that is used when creating a transaction to control who will have access to the bitcoins.

You should create a new one of these every time you receive bitcoin. There are a few exceptions to this rule, primarily when you are expecting to receive bitcoin from some kind of service multiple times and they offer an option to "lock" your payout address as an additional security measure. When you send bitcoin from that 'dedicated' address, it is best to always send to a previously unused address

"Bitcoin Wallet": Software or a service that allows a user to manage one or more bitcoin addresses along with the associated private keys, and typically provides an interface for creating transactions and identifying the total amount of bitcoins under the wallet's control.

Generally speaking most wallet services allow for some level of coin control, however it is generally best to create multiple wallets to promote additional privacy. Even though wallet services allow for coin control, people make mistakes, and you may inadvertently sign one transaction with two private keys that you intended to keep disassociated with each-other, having multiple wallets helps prevent you from making that mistake  

"Bitcoin Account":  A service provided whereby you turn complete control of your bitcoins over to the service provider and trust that they will return those bitcoins to you upon your request in the future.  (Some service providers will misleadingly call this a "wallet".)

I may be incorrect on this, however I believe that some people (including satoshi) at one point called a bitcoin address a 'bitcoin account'. Additionally, today, some services allow the user to retain control of the private keys when creating an 'account' (for example coinbase multisignature vault - the private keys are generated either in the browser or by coinbase - I am not sure which and do not have the resources to tell you which applies - although you will need to trust coinbase enough to believe they will not retain a copy of the private keys after they give them to you). For the above reasons I would dispute this definition.

[countryfree]

Besides what I've already said, if you want to be safe the way I want, it's best to have several wallets, with different software, and to buy your BTC from several exchanges in different countries, wiring money to those from several bank accounts in several different countries.

I also suggest you move several times each year.

[Possum577]

Words have meaning.  Using the wrong words results in causing confusion and making communication more difficult.  Please learn and use the following properly.

"Bitcoin Address": A string of letters and numbers typically starting with a 1 or a 3 that is used when creating a transaction to control who will have access to the bitcoins.

"Bitcoin Wallet": Software or a service that allows a user to manage one or more bitcoin addresses along with the associated private keys, and typically provides an interface for creating transactions and identifying the total amount of bitcoins under the wallet's control.

"Bitcoin Account":  A service provided whereby you turn complete control of your bitcoins over to the service provider and trust that they will return those bitcoins to you upon your request in the future.  (Some service providers will misleadingly call this a "wallet".)

So, I create multiple "wallets" for the same reason that I don't carry my entire net worth of cash in my pocket everywhere that I go. Mainly, security and convenience.  I have some cash on deposit in a bank account, I have some cash in a safe, I have some cash in my pocket, I have some cash in assets, etc.  Similarly, I have some bitcoins in a "paper wallet", some bitcoins in Armory, some bitcoins in Coinbase, and some bitcoins in Blockchain.info.

I create a new bitcoins ADDRESS for increased privacy and slightly improved security.  If I only use one bitcoin address, and I give you that address so that you can send me a small amount of bitcoins, then you can look on the blockchain and see with absolute certainty exactly how many bitcoins I've received in the past, and on what date and time I received them.  If others that sent bitcoins to or received bitcoins from have made their bitcoin addresses public, then you can see when and who I've been sending my bitcoins to, and receiving them from and how many I sent or received in each transaction.  You'll also be able to continue to monitor all of this information about my personal finances in the future.

Hey Danny, great add here. I also want to thank you for finding a solution to your personal frustration with signature ad campaign posters. Everyone, see DannyHamilton's signature, he's made a list of those of us that have an signature ad and ignored us so he doesn't see our posts. That's a great way to deal with it! Another great way to deal with it (if you're sick of seeing ads) is to elect to not see signatures of posts, which you can select in your account profile settings (look and layout).

We CAN coexist and remain productive to the community.

[jeffhuys]

Well, some web services use multiple wallets to ensure safety of their bitcoins. They only have one hot wallet and several cold ones in case things go bad.

[jacktheking]

Like what others said. Normal people create many wallets to avoid lose of Bitcoin if a wallet was hack. You might want to create a few wallets if you have large amount of Bitcoin. It wont help you if you have a small amount of Bitcoin. They fees for transaction (from wallet to wallet) will be very high.

[tss]

lots of reasons.  privacy, security, separating funds, accepting private payments, the list goes on and on.

[BootstrapCoinDev]

Sounds like your PC wallet is the only one you have control over. Coinbase controls all the addresses in their wallet. When you send bitcoins, it's the recipient that specifies the address to use for the transaction. So your only concern is for your PC wallet receiving address.. that you give to folks send bitcoin to you. And yes, you should provide a new address each time for those transactions.

[okthen]

It makes sense to have at least two wallets:
- One for the bitcoins you actually want to spend, in an app like blockchain or coinbase
- A cold storage wallet, for the coins you want to hodl