There's no legal requirement to send a statement exactly, the bank can't force the customer to eStatements, but they can choose not to keep the account open if

There's no legal requirement to send a statement exactly, the bank can't force the customer to eStatements, but they can choose not to keep the account open if they opt out. There's additional complexity around if it's a debit account vs credit account. But usually what happens is the system the bank bought to run their core is setup one way and hasn't been switched for a long long time.