Although not the most powerful weapons available, these gloves were still more damaging than all but the strongest magical weapons (4-37 dmg, compared to 4-34 for a +2 sword and 4-40 for a +4 axe). Their effectiveness might well be partially attributed to the wearer's foes believing their opponent to be unarmed!
Though they were useful indeed, these enchanted gloves fell out of use after Ultima III, falling to the status of collectors' items of an age long past.
If thou lose all of thy weapons, this is what thou hast left. Although it is possible to kill some of the lesser monsters with thy bare hands, the odds of success truly are not very high.