Why - Because I saw a flying egg!!!
http://img261.imageshack.us/my.php?image=eggek1.jpg
I saw one yesterday. It was a Venture located in a hanger row behind mine.
Looked a bit like a flying egg. Guy did a beautiful job of building. After talking to him, I was impressed with the speed (close to 300mph) with the engine he had in it.
Came home and looked it up and became less impressed. Just the kit was $70K, sans engine/prop/avionics/instruments. And now that fuel prices have raised its ugly head again, I wouldn't want to feed that big IO-5 something. Have to say the RG was sweet looking but a bit too narrow for my comfort zone. Also, other than speed - it's got some egg on its face compared to a RV when you look at the specs. If I get a chance to take a ride in it, I'll report back.
As I see more out there, I am so glad I built an RV. I feel like I got the best overall value for the dollar. Speed, performance, versitily, economy, and information help when I needed it.
For no other reason, a future homebuilder should consider the tech support, product availability, and the brain trust that is out there.
One last thing, future builders need to think of insurance. RV's are much easier to insure than other amateur builts and have rates comparable to certified aircraft (tail draggers a bit more).