I have a friend that lives in a nearby city. When I mentioned that I may come to visit (with my bike). The first thing he said was "watch your bike, Amsterdam is filled with bike thieves". So I agree with you, I would not leave the bike outside. I am very surprised to hear you are having so much trouble. Have they given you a reason?

The only two I can think of are:

Dirty tires. Easily cleaned by wiping them down before bringing them into the room.

They get in the way during room cleaning. If you are staying just one night then this should not be an issue since the bikes will be gone when they go to clean it. If you stay multiple nights then you could promise to remove the bikes during cleaning.

It seems that between the airlines and hotels there is a lot of prejudice directed toward bicycles. I just wonder if things would be different if CEOs rode bicycles instead of golfed?