It's funny you say that, actually, because Massive gave the Tommy Gun and M1928 that terrible talent in the same update that nerfed hipfiring into the ground. The gun is being reworked though, but they haven't said how yet.

I'd keep the gun around just in case we get a Ninjabike Bag scenario again and it goes from trash-tier to god-tier.

yeah but why would they make a piece of fucking garbage the third talent
that shit is fuckin trash dog get the fuck out

Because most Exotic weapons come with their own special third talents. They can not be changed. The only exceptions I know of are the Liberator, Centurion, Hildr, and Eir.