Unpleasant as it may sound, it's mainly the olympics's fault. There is no money in track because average people are only interested in it once every 4 years. In the 19th century, track was a very popular professional sport, but the olympics came along with its amateurism and throttled the development of athletes. By the time it threw out the amateur rules, shoe companies were running the show.
The NCAA is no help. They spend a lot of money training athletes but the vast majority will never be paid a dime in their lives, and the few who are still wasted years working for nothing. College track programs generate little revenue because they are poorly promoted and can't compete with football and basketball for the general public's attention. Nobody cares what school beats which in a dual meet, not even the schools themselves. It's all about qualifiers so they get to go far away and lose to someone from the SEC. The public has zero stake in any of it.
There would still be more low-level pro meets if it weren't for road racing. Road racing is much like crossfit, a lucrative business that swindles average people out of millions of dollars by training them for athletic feats of questionable value. There is no money at all in the much more difficult task of training people to run fast instead of far.