Locking the knobs

Why the bed needs to be levelled after some prints? Is it that vibrations from the printer move the knobs?
What if after levelling I insert a piece of foam between each knob and its mount to keep it from moving?

Stronger springers is what I use on my Ender 5 plus. Silicone spacers is another option. Locknuts too. Original springs on my 5 plus were too weak and were like you describe.

So in fact the goal is to somehow prevent the knobs from turning.

Once it is perfectly level I guess the answer is yes. Had someone yank a print off the bed, totally put it out of whack, had to relevel it all, bang goes half an hour. Better that I got a flexi plate rather than glass, easier to remove.