Here's my opinion. Let's call somewhere around the 1:05 to 1:10 range the sub-elite crowd. Now most of these guys are probably guys who have continued to race after college, but aren't good enough to be truly elite and make a living off it. There's no real financial incentive, so they're in it purely for the love of the sport and the desire to continue to improve after college. This probably also makes them some of the most passionate guys in the sport, almost to an obnoxious point. Most of the them probably have full time jobs and train before or after work, maybe with a few other guys in their area in the same situation. Other than the occasional comped entry fee, they're used to paying their own travel expenses.
Now answer this question. How many of your former college teammates, still race competitively and would fall into this category? Probably not many. So why is that? Most have good intentions after graduating and stick with it for a few years, but many finally give up and quit. Why? Because they're either beating the hobby joggers by 3 minutes, or getting crushed by the Kenyans. So after awhile they begin to wonder what the point is. They miss the college cross country atmosphere where there's 15-20 guys around them in any given race that they're dueling it out with. It's hard for people to continue on their own in that situation when it's purely for their own enjoyment. So they quit or become hobby joggers themselves. And then the pool of guys in that range gets even smaller for the guys that remain, and the vicious cycle feeds on itself and continues. That's why these guys are often in no-man's land, essentially doing time trials. There's just not enough guys in that range that stick with it.
So why did Houston decide to eliminate some of these guys? I'm sure money is some of it. But my guess is that somebody was lazy and just didn't want to deal with them. Having to answer their e-mails and verify their credentials and stuff. And like I said, these guys are some of the most passionate, so they might require a little more attention. Not to mention that the true elites probably have a coach that handles all the logistics for several guys, so it's easier for the organizers to deal with 1 coach and his many athletes, and not have to deal with the many individual sub-elite athletes themselves. So they don't let them in, which is even more discouraging to these guys because they feel like they're never given a shot, so more of them quit, etc. etc. You get the point.
And so the post-collegiate sub-elite runner continues to be the stepchild of the running world that's no one wants.