In response to some of the comments above, I'd just like to say it again, Space Engineers and even Subnautica really do ship / sub interiors right when it comes to the gameplay aspect of things, especially maintenance and damage control.
For example, in Space Engineers even minor damage requires your attention. If the hull is breached, you'll lose your internal atmosphere, which isn't the end of the line in the middle of a battle (think of a blown canopy in ED), but it will definitely warrant your attention after the battle is over. Searching down and welding that breach is great fun IMO. Sometimes, thanks to a marvelous damage model, that breach will be a HUGE hole in the side of your ship, and you'll just stare out in amazement through twisted metal as air rushes into the vacuum of space. Damage can also take out subsystems and conduits connecting those subsystems, like individual thrusters. All of the sudden you're drifting to starboard because those lateral thrusters have been either damaged or loss power / fuel due to a destroyed conduit. This changes the flight dynamics dramatically, but assuming you survive, you can then go back and patch things up "good enough" to get yourself back your base. These repairs may be done from inside, or they may require an EVA to do repairs externally.
As for walking around the ship when not in damage control mode, my ships often have laboratories where I can do experiments while my ship is in a long flight. Or in a game like Subnautica, there is periodic maintenance like changing batteries, managing inventory (in both SE and Subnautica, resources are kept in actual lockers rather than magic invisible material bins like Elite), getting a bite to eat (hunger and thirst are part of Subnautica's gameplay), working on my miniature vehicles (mini-sub, SLF, SRV, etc), and so on. There is a TON of gameplay to be had here, and this added gameplay really makes my ships feel like characters in their own right.
Just imagine if the pilots and crew in Star Wars and Firefly never left their cockpit sits. Imagine if Han Solo or Kaylee just pushed the AMFU button rather than have to go back and fix things with their own hands.. Imagine if they never went into the common area to share a meal or play monster chess. How boring would that be!