Shuttles give an expanded range to market interactions. Other fleets get to interact with a market while in orbit of it, it'd be nice & give some extra useage to shuttles if having a shuttle allowed a player to do the same, especially in conjunction with the weirdness of burn drives, IE if your burn-pass misses a planet rather than having to drag yourself to a stop and then go back, your fleet could just brake & (abstractly) send a shuttle to the market as long as the market is close enough that if the shuttle got attacked on the way the fleet itself could aide.
And, note, I'm not suggesting we get fleet-splitting. Just an expanded range at which you can interact with a market, and anything else your shuttles can do by themselves (surveying if they have survey equipment, potentially allowing a large fleet to stay out of a magnetic storm while surveying?)