As a scale modeller I have being wondering that how come there are no TF-model kits? There are just few, but all in all there is like 2-3 model kits and all of those have being sold out long ago.
Don't people like building their own model kits? Sure, they can't transform, but there are tons of TF-figures that can't transform and folks buy those. The good thing with model kits is that they can be super detailed, and you can paint them yourself. I think all Gundam kits are made of colored plastic, so you don't have to paint them, but you can. With an airbrush and with a little practice, you can made them really cool. And even if you would buy an airbrush, it would be cheaper that buing those ultra detailed statues that are like 800-1500 dollars each. I bet that model kits would be cheaper, even the higher grade ones.
The non-transforming factor is likely the biggest culprit. Normally takes a pretty high-end piece to get over with the community not having that gimmick. On the other hand, Sentinel is apparently doing some kits (unk when they release.) I remember they showed at least Optimus Prime at Wonderfest.
Also, there was an God Ginrai resin kit that was a Wonderfest exclusive at some point, but no mass-released items that I can think of. I have a ton of 1/100 kits and I agree with your general sentiment.