Its not bad for them. Its just a hell of a lot more upkeep. To make wax work you need to buff it multiple times a year/ strip and reapply.

Polyurethane was developed as hassle free.

This is an extremely short and concise explanation. I could go on for pages why wax sucks. Imho

Buff on a coat of wax and you will be doing that almost for the life of the floor. It may make refinishing the floor with a film-forming polyurethane very difficult, as wax residue may interfere with adhesion of sealer and urethane. There are ways to prevent peeling in these cases, but waxing will make for lots more work if you ever want a new polyurethane surface.