I'm guessing that some pay by e-cheque because they think it will be marked as paid & the seller will send as normal before it clears or not.Possibly the same thing with bank deposit.Buyer marks as paid doesn't mean it's paid.I know a seller that has had a few bank deposit people who expect the item to be sent as soon as they mark as paid.Many of them string it out,probably waiting for free items before the unpaid item dispute starts.

Maybe I'm just feeling cynical today.