I think musicians who are familiar with spending hundreds of hours studying and honing their craft are attracted to the genres of music that are known for superiority in craft, such as prog rock.
I also believe that, because of its advanced technical nature, prog rock attracts people who are more technical in nature and who are not neccessarily musicians. These people need to be aurally fed something a little more challenging then radio slop. Either the music, the craftsmanship, the lyrics or the sounds need to be comprised of substance to dig their intellect into. So, even if they don’t exactly know what technical things are being done, as a musician might (like whether it’s in 9/8th time, or the guitarist is double picking 32nds, or the synthesis is running his Synergy through Moog modules), they are attracted to the fact and appreciate the music because it is ‘intelligent’ in some or all ways.
I play piano - See
http://www.simmphonic.com
My alter ego plays percussion perpetually probing for a fresh groove -
http://www.simmphonic.com/cow/who_is_cow.htm
and for a little geek action check out -
http://www.simmphonic.com/programming/flash.htm