Pmayjr,
No, it's not too much to ask, but you're right; it's a pipe dream. The two major influences in racing are gambling and breeding, and those two industries are completely independent of each other. The only way I can imagine the average fan influencing the decision of when horses should be retired is if every person who gambles on races (or at least a sizeable majority of them) agreed to unite and boycott all the big stakes races until the NTRA imposed some sort of nationwide rule about what age horses have to be to breed. Otherwise, it'll have to be up to the racetracks, if they ever start to care about declining attendence, to push for something like that, and I just don't see it happening. But I'm with you; it'd be a big deal. Heck, I'd push for 6 years old being the minimum age for a horse to breed.
Cannon is right; it's a gambling-driven industry with no money to be made in merchandising and licensing. As fans, we just don't have any economic clout to influence people to keep their horses in training. And gamblers are in it to pick winners and make money, and that has nothing to do with whether Street Sense runs at 4.
Though yeah, greedy tracks cutting the percentage they take would help, too. I also think a few months of the year where there is no horse racing would be good, too. It's harder to follow a year-round sport than one that runs a limited number of months per year.