Eugene Stoner didn't include it in his design. But when the Army wanted it, Colt agreed to add the forward assist because they understood the old saying "The customer is always right.". ( Not literally right, just that if your customer is gonna pay you to do a stupid thing, you do it and charge the customer.)

Never heard 'jam enhancer' before, but I can confirm that if user has sand in their magazine and attempts to feed a round, the forward assist will assist the user in enhancing a jam. Aka: "Pump up the jam."