Monetization doesn't enter the discussion for Frontier when it comes to ship interiors. I think (ie this is speculation based on opinion) that there's three factors preventing ship interiors.So with ship interiors, I'm sure many of us have asked ourselves, 'what would it take for Elite to introduce ship interiors'.
The obvious answer? (especially now): The opportunity for monitization.
1) The ship models themselves can't accommodate an internal layout. Features like the SRV bay and SLF bay are located in spots which, on some ships, are literally right behind the door at the back of the cockpit. You can't open that door and have an SRV blocking your path.
2) The code for Elite Dangerous is (from what I've seen others say, those who actually know programming) a mess. It's original code that has been patched up and patched up and patched so many times that making simple changes either breaks things that shouldn't break or makes the game very unstable. We have to remember, Elite Dangerous isn't using an industry standard game engine like Unreal (for example), so every time Frontier hire a new employee to work on Elite Dangerous, they have to learn Frontier's Cobra engine.
3) It would take a lot of work to design and plan ship interiors, it would require model changes, it would have to incorporate some level of new gameplay (yes, I know I often say it doesn't need gameplay, but I'm looking at this from Frontier's POV, not my own and they'd have to have gameplay in there for interiors). And it would require someone to decide if it's a free update or its own DLC on a level with Odyssey. Frontier would have to be ready to handle negative feedback (because there are many in the community who would be negative towards this no matter what). And taking all that into consideration (again from Frontier's POV) Frontier probably think it's easier to simply not do it. This is also probably the same reason we don't get landing on atmospheric planets.
Don't misunderstand me here, I would love to have ship interiors. I truly believe Frontier could do it if they decided to, but I simply don't believe Frontier have the motivation to do so.