I'm sure the reports have piled up over time and it's not serving any purpose to still be using them, the worst nightmare of P2P is to lose your money because you sent it out of your bank but the recieving bank doesn't get the funds for over a week, no one will want to release their coins if they haven't received payment for it and even though people know these banks are reliable they will still keep using them so the best thing the exchange can do is to make sure no one can use these banks again on their platform.
Delayed bank transfer can do make P2P trading stressful due to the seller may not receive money on time. On the other hand while the bite is waiting for the BTC to be released. I believe that the removing payment methods that do keep causing these problems can make P2P smoother and also safer, this may reduce the number of available options but reliability is much more important than having many payment methods.
It's simple, it's better for them to work with 2 banks that are always reliable then to work with over 20 with no reliability. The better the P2P experience the more people will want to use it so while it's to make P2P easier for people it's also to make sure they don't end up losing people to something like this that could have been avoided.
It's the same with how scammers were everywhere on their P2P platform, looking for ways to get money from buyers and sellers alike, you will hardly see them today and they worked on it because they were losing users because of it.