Modifications
As soon as heroes get theirs hands on a starship, they want to modify it. The desire for faster hyperdrives, more weapons, better shields, and possibly even some space for smuggled goods generally comes before the first payment to a Hutt loan shark is due. Upgrading and modifying a starship gives players a sense of ownership that makes them more connected to a campaign, and it serves other useful purposes as well.
Heroes who want to improve a starship have a built-in reason to take risks to earn credits (or other re-wards, such as the use of the repair bay of a grateful military group). Although Star Wars focuses on on heroic action-adventure over the cobbling together of credits for tinkering with a ship, many characters are simply more motivated if they know there's a material reward on the line. Furthermore, a starship acts as a base of operations, allowing heroes to have a place that seems like home even as they gallivant across the galaxy. Finally, as the heroes gain levels, a better-equipped ship prepares them for greater challenges.