Thanks for your input on this....
This raises some interesting issues... primarily is the EV3 an embedded device that has a useful but reasonably limited set of functionality (in the case of leJOS a platform to run robotics programs written in Java), or is it a general purpose platform that is intended for people to hack away with as they see fit. Clearly Lego intend their version of the firmware to be the former, the rPi and arduino are very much aimed at the latter. At the moment leJOS is based on the Lego firmware, there are other projects out there which have started from a different perspective and which may be more suited to your needs at the moment. See the the ev3dev project:http://hempeldesigngroup.com/embedded/tag/ev3dev/
Both approaches have advantages and disadvantages (so for instance ev3dev does not have particularly good support for sensors, motors etc. I'm sure this will change). Over time they may move together. However things like having a general purpose disto as your base does have an impact on things like memory usage etc. As already mentioned the Lego/TI distro use busybox for pretty much all of the user level commands and daemons. ev3dev uses separate more fully functional stand-alone programs (if you don't understand this please google and read about busybox and how it works). For many uses of the EV3 this may not be an issue as there will be plenty of memory, however for leJOS that may not be the case. 64Mb is not a lot of memory for a system running Java SE. We also like to do as much as we possibly can in Java (so that as much of our code is accessible to our users) which means we want to be able to run multiple Java applications on the device, so memory usage may become an issue for us.
Finally it comes down to the people involved, their time and their interests. Doing things like using yum and having the back end repositories all takes time/effort and skill. At the moment the leJOS team is concentrating on getting Java working well on the EV3, supporting the huge number of sensors out there and generally building a good robotics development platform for a wide variety of end users. If people want to do things outside of this then that is cool, and we would be more than happy to see this sort of thing added to leJOS (so long as it does not compromise the other aims), but it needs someone to do the work, contribute it and support it. Personally I'd rather be spending more of my time building and writing Java code for some cool robots rather than managing a Linux distro (or even contributing/working with someone else's!).