Is there ever a reason to have multiple bank accounts?

Solution 1:

Bank accounts are useful for setting up bounces. If you create an account, obviously you have that account on the system, which makes the bank more valuable as a bounce node (dotted line around it; takes longer to process). Your log-in credentials will never be revoked, either.

You could of course hack an existing account, but creating one is much easier and does not start a trace, so this is useful early in the game.

Solution 2:

Having a bank account will make stealing money from it much easier, as there is a very brief window of opportunity for you to delete the log of both sending and receiving money. Not having to connect to another bank to do that is very helpful.