Are there other reasons? P2P is certainly not necessarily cheaper, so why do people use it?
Mainly because they want to avoid stuff like this that happened yesterday. You may say it's not a big deal, I can wait later to get my money out, but it may happen when you need the money asap, like it happened to one of my friends yesterday. He planned to pay for some service which was important for his business, but he couldn't do it for hours, delaying the work for a whole day.
So yeah, not a smart thing to use Coinbase/Binance or any other centralized exchange to store your crypto. At least not a big amount, and especially not for too long.