to save money ?
Surprise they have not yet done an all white plane after delivery....don't you think that would save money? or a bare metal livery..
Also makes the aircraft lighter thus reduce MTOW, reduce payload and burn less fuel...
I think that would be the fatal move after all Ryanair's cost cutting measures
(e.g. sticking csafety card behind seats, removing reclinable seats, having to ask for you barfbag, crew not being able to charge their phones on board, crew having to pay for water on board, pilots only having one piece of paper per route to prepare it, etc)