Well..
The droid 4 targets a very specific niche market.
If you observe the trend--physical qwerty phones have been on a decline since the droid1/G1. Because of that, no manufacturer wants to make a flagship keyboard phone (for fear that it wont sell as well as the thin slabs). In addition, more and more people have become accustomed to using onscreen keyboards, and some people have never even used a physical qwerty.
Also, motorola seems to think that having a locked bootloader will somehow still attract people... so it steers developers away. Granted there are ways around it now, but that is because of VERY VERY talented and dedicated developers who wouldnt give up.
Personally, I've had both and I absolutely LOVE having a qwerty keypad. But you must understand that the demand for this phone is lower than most--with other phones like the Rezound, Nexus and Razr (all marketed to different target niches), I'd say the droid 4 is overshadowed.
Thus, the developer base is also lower. We're lucky to have people like hash and myfishbear (as well as many other very talented devs), otherwise we'd be nowhere. Also, flashing roms is only cool for so long, after a while you start to desire a stable rom and a solid functioning phone and I think it is safe to say that the droid 4 is just that. Solid, well performing phone that is stable (I'm running eclipse), that has an amazing keyboard.
If you want to be a flashaholic, you should jump onto another niche phone, like the nexus.