Part of the problem is that providing pre-compiled gems is a HUGE pain for developers. The gemspec's 'platform' strings change every now and then, so a gem precompiled and published with Rubygems 1.x will not be found by Rubygems 2.x etc...

The rake-compiler project tries to address this, but at this point I'm not sure if I am any better off than people who waste their lifetime in autoconf hell.