This is not a UPS-only issue. It is simply the way parcels are handled, have been handled, and will always be handled, especially as we continue to insist on speed, Speed, speed, Speed, SPEED!! (For a bit of humor, see if you can find a copy of the old RR story of the Baggage-smasher competition.)
You can't prevent it by boycotting sellers who ship UPS--or any other mode. Boycott the sellers who can't manage to pack well. FWIW, I leave a comment on the quality of the packaging on every piece of eBay feedback I give.