Also remember that for an airline like KLM, it's more difficult to have a generous hand baggage policy.
With Ryanair, you'll be flying on a 737NG, with a uniform overhead locker maximum permitted weight.
With KLM short-haul, you could be on a 737-300, -400, -700, -800 or -900, or an ERJ, or a Fokker of various flavours (unless they've managed to get rid of all of them by now). All have different max weights for overhead lockers, and aircraft can be substituted according to demand. So, you have to go for the lowest common denominator (and allow gate-check for the props - KLM are actually very good at this).
But yes, I also find myself particularly annoyed at the DYKWIA types who insist on taking the kitchen sink on board with them, and blocking the lockers for everyone else.