They are not. When you come back from work after a 12-hour night shift the last thing you want to do is managing your bank accounts. You just want one account to work, and to work well, if possible without the bank screwing you too much.
We're not money savvy people particularly, however my girlfriend and I both have 3-4 bank accounts (UK based, it takes <1 hour to setup a brand new bank, from start to finish).
We have a couple of traditional banks, and then also some more modern "internet" only banking (great for travel with their zero conversion fees, and more granular tracking of spending).
This seems to be the norm between all my friends also.
I have 3 accounts, one for salary deposits, one for bills and one for spending so that I always know bills are covered every month without thinking about it and my "fun money" being pre-allocated each month helps me be mindful of my spending.
Since moving to that system I've been able to save significantly more each month.
I have an online centered account and a local one, they serve different purposes.
Multiple accounts in use greatly increases the chance that you have the money but it’s in the wrong place.
Have we gotten so deeply nested that we've forgotten the title of the thread?
I too have multiple bank accounts, mainly because in the case of bank failure your deposits are only guaranteed up to something like £80k.
Also, in the UK basic current accounts are free, I doubt this is the case everywhere.
I still have one main account that my wages go into, and all bills come out of. The other account is just a backup.