[zeruch]

I think one reason might be that most tortillas in supermarkets are processed to death as well. Most won't go to a solid Mexican grocer and pick up the good stuff (or it's not available) and to top that off, one thing I've noticed outside of California at least, people double wrap small amounts of food in tortilla, instead of loading up, so they eat 2-4x more tortillas than 'normal' (I'm biased because I am in California and grew up here, we understand tortilla physics and tensile parameters, YMMV).

Whether they are "better for you than bread" depends a whole hell of a lot on the bread, and how its made.