Having done those DVCs for Flight Simulator (wow, that was 10 years ago now... now I feel old), I can tell you first hand just how much work goes into making even a basic one, let alone one that lets you interact with it.
The problem with virtual cockpits is that, unlike an external model, well, first is the fact that you need to model it from the inside out, which may sound like it wouldn't matter but it does make a difference, and most importantly, unlike an external model which maybe takes up at most 50% of the screen (the rest being scenery), the VC is a full-enclosure model, which will take up well more than 80% of the view space, if there's a window in sight, and up to 100% towards the back walls and other directions. You can't look away from the interior, you can only look towards other areas of it, so every surface needs to look good.
That means your internal model needs to hold its own under close inspection to a much higher degree than an external model. If you zoom in too closely on an external model and start to see where the detail ends, you usually instinctively know it's time to pull the camera away. On an internal mesh however, that's not an option. The threshold for quality (the point where it doesn't look flat out terrible) is much higher on an interior model, as you can't rely on the scenery.
What more, usually cockpits and such environments are crammed full of equipment, gauges, buttons, knobs, levers, cabinets, lighting fixtures, vents, wall paneling... And to make it look habitable and less dry, you also have to include some 'ambience' details, like signs of human presence (we are messy creatures), like papers, notes, containers, general signs of wear and tear.
On an external model, a lot of these details would also apply, but if they're not there, it's usually acceptable. On an internal one though, on a good internal model, if those 'props' aren't there, you'll get the feeling something isn't right. Like I said, the threshold for quality is higher.
This is why most addons have no interior meshes of their own, and we can't fault the authors for that. They really are a LOT of work, and I'm not even getting into the extra work of making those interiors interactive. That's a whole other can of worms, since compared to the relatively simple task of drawing and simulating input on a 2D instrument panel texture, making instruments in 3D, and clickable 3D buttons and knobs, is a whole order of magnitude in difficulty. Let alone even when you have to mix 3D gauges with 2D graphics, like MFD screens. I'd call those 5D gauges actually, because apart from the 3D space the screen itself occupies (XYZ), you also have to render the graphics themselves in another 2D canvas (UV), so you've got 5 spacial dimensions to handle there (thankfully the second set doesn't have to be orthogonal to the first three, hehe).
And here's the fun part, this is all just to develop an eye-candy interior model, even with animated clickable bits, if you really want your buttons, knobs, gauges and screens to actually control stuff in the ship, then you have to get down to programming their functionalities, for each and every clickable thing, since they are each supposed to be doing something, otherwise there wouldn't be a switch there.
This is probably quite long a post already, sorry if it sounded a bit harsh, I don't mean to lecture here, just to inform of the many factors that go into the making of an interior cockpit view for a flight sim. As you can see, it's a LOT of work.
All that said though, there are quite a few addons with wonderful interior models however, and props to all those who put in the effort to make them!
Cheers
