A shame that we have to pay for something that is only fun for RP and does not really have an in game function!
Actually, it DOES have an in-game function. Visiting your ship interior is the only way to get certain special Duty Officer assignments, such as the Tactical Special Projects and Culinary/Bartending assignments. Those assignments and similar do things like generate supplies, consumables, and even cool new gear.
The ship interior is also the the easiest way to switch to a small craft for certain missions and events.