If the bicycle industry were truly savvy, they would provide about three times more attachment points for accessories. Dropouts would have three threaded holes for accessories instead of one or two. There would be threaded bosses along the sides of all the main tube, light attachment points along the seat stays, etc.
Few of us would be able to resist buying one or more accessories for every attachment point on the bike even if we don't actually use them all. (admit it, you know this is true) Since accessory markup is much higher than the markup on bikes, the LBS and manufacturers sell lots of new accessories, make more profit, and stay in business. You get even more toys to choose from and lots of discussion on the boards over which on-bike beer brewing system works best.