Two reasons.
One. Communist. You know the deal.
Two. This would highly encourage players to play the USSP. As not having to worry about the constant cost of ammo, ships, and other such. Would encourage players to play them. USSP are meant to be more of a numbers faction, though in game this is completely untrue a lot of the time. This would make the USSP a safe financial bet with less risk of losing a ton of credits.
They would gain tickets annually, or be given out by the Commissar. Who receives a bonus to be distributed by the powers that be. Something like ammo would be one or two tickets. While a ship would be a lot more.
They could, much like FMC, be made into credits. Though this is mostly done by the Commissar to pay any any USSP who request such. Or more importantly, any spacers who would want to join the cause for the benefits. There would be some kind of official system to enlist players into the USSP as workers so they begin to get tickets.
It should be noted alot of vendors in Camelot would have be reworked. As only one vendor is really USSP specific. The ammo one.