1. Traditional athletics is not easy to follow live. Big gaps between races and very hard to follow field events properly as there are always other events to distract away from them. Field events over the other side of a stadium are nigh on impossible without iron concentration and a good pair of binoculars. Unless you are sitting very high up or right opposite the finish line it is often impossible to tell who has placed where in a race or to see how it unfolds. These issues also translate to live TV coverage unless it is done very well.
2. The statistical nature of the sport enables casual observers to say that X has run 0.6 seconds slower than Bolt so he can’t be much good when in reality X has just turned in a pretty good performance. Unlike many other sports, performances are measured by the watch and the tape as well as against competitors.
3. Linked to 2, it’s the nature of the beast that any sport that gets good TV viewing numbers is elite level. And even there, DL would get major channel prominence if broadcasters think it would get the viewers. It doesn’t so why think domestic level stuff, irrespective of format, would?
4. And we also have to accept that some athletics events are simply more spectator / viewer friendly than others, particularly the sprints, some jumps, and even the throws where the athlete is always straining to do their best with, sometimes, spectacular results. That isn’t the case in distance where, say, Mo can win many races running completely within himself, and I suspect that many causal viewers wouldn’t be remotely interested in 27 minutes of “jogging” followed by less than a minute of excitement. There’s none of the potential immediacy of a crash in F1, a knockout punch in boxing or a wicket in cricket etc. Distance running is tactical, strategic and demanding, but not televisual.
None of the above is to say that new ideas shouldn’t be tried, but I just think it is very very difficult. Gimmicks tend not to work, although T20 cricket is an exception, but there the popularity (apart from the betting) is down to the likelihood of something spectacular happening each and every ball.