I think its more of a case of "why bother". As pilots we're not permitted to carry out any real work on the aircraft, so whats the point.
If I were allowed, I'd be happy to carry out all maintenance on an aircraft I owned, none of it is rocket science, and with the right tools and manuals, most jobs can be fairly easily done. I'd leave the big jobs to the professionals, just becasue they do it all the time, and can often do it a lot faster. (like changing a clutch on a car, although its fairly straight forward, and I've done it in the past, I'd rather pay someone to do it now, who has all the right tools / facilities etc.).
EA