You may want to hide an account when it becomes obsolete because you pay it off or close it, yet you do not wish to delete it because doing so will affect transactions in another account. An example would be that you paid off a loan using your checking account and if you delete the loan account, the transactions in the checking account would also be deleted, leading to balance inaccuracies.
By hiding accounts you no longer use, you keep your transaction history but you do not have unused accounts cluttering your lists and reports.

