too hard to tune? too lazy to tune! try tuning my Spanish Laud which has 17 strings. Or my Harp which has 31. Or my Autoharp which has 35.
Or a Hammered Dulcimer which can easily have over 150. Or a grand Piano which has about 230.
   Most 6 string Guitars I see being played have dust. Many players of various instruments never clean their instruments. I've seen dust under the mechanisms of woodwinds, brasses, & percussion instruments-also lots of tarnish. I've pulled all kinds of things out of instruments including pianos, such as combs, papers, pens, pencils, baby rattles & other toys & things which can't be mentioned in polite company.
Sometimes people are just too lazy to do alot of things. Laziness may be the one thing that keeps some people from playing 12 stringed Guitars.