Hexes are great for climbing in the mountains. Great if you have to leave something behind. I have placed my share.
But.....
Come on down to Beacon and try to climbing there with a rack of hexes and tri cams, not that you cant....but a rack full of cams makes things alot easier on hard climbs. (SE corner excluded)
Look at all the top trad climbers in the world or your back yard. Do they have a rack full of tri camms and hexes? No...they sure do not.