I think the blame goes back to runners' schedules and irregular racing patterns. How can you watch them on TV if they run a few times per year, frequently don't show up to something they announced they'd appear in, and then often do show up in things unannounced or declared within a week of the meet?
I think you made a great point.
Back in the 80's, when road racing really started to take hold, there were guys who raced the 10K "circuit" almost weekly.
They went from city to city, were "up close and personal" with the runners after the race and were often on TV.
They weren't household names, so to speak, but everyone knew who the top runners were.
You watch football every week for 20 weeks or so- the same names over and over.
Imagine if Tom Brady played in 2 football games a year?