Given that you run a big shop with a lot of payment methods, some of the payment extensions bring a lot of unneeded/unwanted payment methods with them which appear in the payment method list. Of course you can generate a list and hide them via custom xml (at least in M1), but it's not very handy.
Edit: To get an idea what I mean:
Currently we have a shop which has 68 payment methods in this list.
These 68 payment methods are added by 10 payment extensions whereas one of them brings > 20 possible payment methods.
Only 8 of the payment methods are currently activated in the shop frontend.
This makes the list quite confusing.
The list under Configuration > Payment Methods can get quite long so I'd like to suggest to either