Credit card fees are exactly the reason why the switch happened. Do you really think the washing machine companies would bother building an app when they could continue charging without any investment whatsoever?
The cost for a vendor processing CCs is something like (iirc) 3% of purchase price + $0.10. The benefit to vendor of selling you credits (aside from the fact that you might not use them all), is that they only have to pay the $0.10 portion of the fee once for every, say, $20 worth of washes instead of paying the flat part of the fee every single wash.
intermediation. they get a chance to have their own laundry bucks currency. they get better tracking. they get to show you ads, and have marketing touch points with you every time you need to do laundry.
