I'm quite surprised that in this statement, you're making the same mistake as an average uninformed player would do.
Everyone who knows how game studio development works, or at least everyone (like me) who's read about it over several years knows, will tell you that the "devs" who work on car wrecks and doors, are not even in the same field of expertise as the ones (like faatal) who work on AI and drivable vehicles.
Also, consider this: we're nearing release! Yes, I know, it's probably still a few years away... but my point is that TFP are now, IMO, in that part of the development cycle where you start making all the hard decisions. Time is limited, and so are dev resources. People are becoming more and more impatient, but you need to finalize the remaining systems the way you want them. So, on one hand, they're refurbishing the crafting system because it makes more sense than the current one, while on the other hand they also need to lock down the systems that are not ready for release at all (like water).
Considering all this, it's no surprise the devs are not going to add more vehicles or improve electricity or add more zombies. These are all system that already work ok.
Maybe in the future, after release or even during Beta, they'll actually ADD more stuff to the systems that work. But that won't compromise HOW the system works, it will just add more cake types to the selection.