I say this as a former bike racer, and someone that has watched most, if not every minute of the televised TDF coverage for decades, but the reality is, watching a live bicycle race is pretty boring. Televised coverage adds to the intensity, adds variety and drama, fills in the details about history and nuances of the sport, explains the tactics and rivalries, etc. etc.
But a live local race is basically just a bunch of guys pedaling their bikes around......and around, and around, and around..........
The average American doesn't know bike racing from Shinola. Most anyone in our culture can follow a baseball or football game along with everyone else in the room, even if they're not any kind of enthusiast. This isn't the case with cycling.
And even for those of us that "get it", and have even done it, there's just not a lot to sink your teeth into at a local bike race, therefore not a lot of folks are inclined to pack a picnic lunch, grab the kids, and go make a day of it.