Google your state code, for example "Arizona Landlord Tenant law". Some states address carpet cleaning (who pays or is responsible). If replacement is addressed (iffy) that's where you'll find it. (Other than the lease, if it's even addressed there.)

AFA #2 a local or county heath dept could answer that, if they address it. But 2+ yrs under 'normal wear and tear' is not an old carpet by a long shot. Unless it's just been abused and ruined, a good thorough cleaning could renew it.

Some apartments have their own rules about this. Every place I've lived, they've cleaned the carpet before I moved in, but not replaced it. Friends of mine got dinged on their security deposit once because they vacuumed carefully, but didn't rent a steamer and clean the carpet before they moved out--of course, the super never told them they had to do that, either.

Now if the carpet were stained or torn, I'd expect a good landlord to replace it. Dents from furniture--those will usually gradually fade out, or you can google and find several methods of erasing them.

But I still have memories of my very first apartment hunt, where there was a hole about a foot across in the middle of the living room carpeting. "The landlord's going to fix that, isn't he?" I asked. The guy showing me the place looked very startled and said, "No. Why should he?" Needless to say, I didn't rent the place.