I'm not sure how valid your argument is here. In my experience as a solutions architect, the companies who can afford support will end up buying it simply for the peace of mind. Smaller companies who can't afford it, wont buy it (with or without the nag screens).

Secondly, if someone is building from source, chances are they're smart enough to realize there are many ways to remove those nag screens if you just think about it for a moment. I've personally removed all the "nags" on my lab server since I have no need/use for support, however, if a client wanted it I would happily recommend it.

Lastly, In my opinion those nag screens only push people away from a technology and find alternatives (i.e. Proxmox).

Food for thought.