BTC I was wandering with bitcoin core, I have 50% storage free in my drive C:/, then I was installing bitcoin core, then I sync it to the network, When I browse my drives I saw drive C:/ on red alert, and I said "what happen?" I'll checking the storage and I saw the reason, bitcoin core sync downloading all blocks and data with more than 30GB capacity stored in my drive C:/, now I'm asking myself,
So your local drive is only 60GB? Just asking, not judging.
"why should I depend in local bitcoin wallet?" I can store my bitcoin in online wallet like in blockchain, right?
There is a middle ground between the extremes of storing a complete copy of the blockchain and trusting a 3rd party. Slim or light clients like multibit (HD) or electrum (2) do not require you to download the entire blockchain, but still run on your local machine without you needing to trust someone offering a wallet service.
Maybe if that would be, I have to purchase a new computer for bitcoin wallet storage and bitcoin mining only,
Mining with a computer is dead, if you dont have specialized hardware dont even bother.
What is good for you and for us? what is the purpose being depending the local wallet?
What is good for me might not be what is good for you. Thats why there are different solutions, not everyone needs bitcoin core, but the network certainly needs to run full nodes. Without full nodes some client can not gather the data, without full nodes miners cant mine and without full nodes your transactions cant get relayed to miners to get a confirmation. The purpose of depending on a local wallet is that you do not need to trust someone else with your money. You only have to depend on yourself and your security practices. This is certainly not for everyone, but with bitcoin its possibility.