It is illegal in some countries to buy/sell bitcoin. Some banks bans accounts that try to transfer to crypto exchanges or block transfers. For them localbitcoins is the only place to find seller/buyer.
In countries where cryptocurrency is illegal, people have to go to direct tradings with trusted people in their communities as same as in the forum. The trusted people will not go first. Then, P2P marketplaces are one of best options for locals.
In my nation, people can choose
Remitano,
Paxful or
Bitcoinvn.io. There are a few others but they are smaller.
You are also able to buy/sell without KYC, and without any trace. Anonymity is a tier 1 thing for some.
It is wrong. If you have to open account on P2P marketplaces, and have to leave your bank details in trade chat, you don't have anonymous trades. Another contributor to destroy your privacy and anonymity is KYC.
Some people prefer to buy/sell bitcoin through peer-to-peer platforms(such as LocalBitcoins) for privacy purposes, for some reasons like preventing your local bank from knowing that you're an active buyer/seller of bitcoin or something similar.
What you said is true when people believe they will be totally safe on P2P marketplaces. In fact, it is not correct all the time especially in nations where buying/ selling bitcoin or cryptocurrency are illegal.
In such nations, if you have trade with a payment method is bank transfer and the trade partner has bad flow of money (from money laundering, ie.) when the victims of those guys report issues to local police, and police steps in, you will get troubles. Police simply contact you and retrieve fiat money for the victims. Bitcoin trading is illegal so you don't have rights to ask for refund in
BTC. You will lose your
BTC and you will never want to get troubles with police.
On P2P marketplaces, choosing
good trade partners is the most important skill.