The problem with high gloss polyester is just what you're finding: it shows every possible defect and scratch. It's not that it's not durable -- it is -- but it really isn't that hard, compared with things which might be around to scratch it. Such as: hard dust (very fine sand, for instance). Paper clips. Staples. Watch bands. Rings. A drinking glass.
I regret to say, however, that I have no useful suggestions for keeping the problem from happening. My own piano is a shellac finish, heavily waxed with black furniture wax. Not, ultimately, as glossy. Much easier to care for!