Same for selling, excluding the fact that they take a quite large % of your amount.
I guess that's why many people come to this forum to do exchanges between BTC and other currencies
So if you can get to own a Bitcoin, trade it and sell it without KYC, why bother verifying at all? I know some people who've verified their accounts although they trade under $2k a month.. this is called just giving away your personal info without a reason for it!
It doesn't matter if they never think about the importance of personal information. Some people will go through the verification steps as soon as they create an account on an exchange, I think it's a habit.
The only exchange that I think we need to verify for regular use is Bittrex. I no longer use it because of the transaction limit, but a few years ago it only allowed a maximum transaction per day per unverified account of 0.4 BTC. Obviously, for those who trade regularly there, 0.4 BTC is not enough and they will do the verification.