I think any sport as involved as Formula One is in the world of technology, engineering, and head splittingly complicated things like aerodynamic properties, CFD models, and tire graining will lend itself to becoming irrelevant in the eyes of the average sports fan.
People watch sports for the true drama and accomplishment that sport provides. I'm not saying that Formula One doesn't provide that, but it just doesn't provide it as well as it could.
Formula One, teams, drivers, and engineers are the best at what they do, but what they do is foreign to an average person it might as well be rocket science. People struggle to understand what taking a turn at 5G means, but almost anyone knows what it feels to score a goal during a football match.
And more often than not winning a Grand Prix isn't predicated at all on driver skill, but just circumstances surrounding that driver's skill, tire performance (prime or option), another foreign term, to most who don't obsessively follow the term, fuel load, and the other team's pit strategy.
But some people will say, Daniel why are you picking on Formula One in particular?
Because Formula One really does have that as a core problem, unlike Grand Touring, Touring Car, Motorcycle, or NASCAR racing, the casual appeal to Formula One is minimal.
I watch an American LeMans Series race, and I know who I can support and who I "despise." I like the Corvettes and Ferraris while the Porsches and BMWs could crash out on the first lap as far as I care. The same applies with WTCC, BTCC, MotoGP, and even NASCAR. I have loyalties and they're much easier to express with those series.
While in Formula One, the Renault R29 or a Toyota TF109 have exactly what in common with a Clio or Corolla? I say nothing. Formula One, more often than not, devolves into some sort of spectacle straight out of "Old Europe" where nationality is the most important thing.
Why else would they display those flags and play the anthems at the podium?
So Formula One is an extremely enjoyable experience every other weekend for six months for the people who really care about the sport. Where you can love your driver and hope that other guy crashes, but for the casual sports fan, they don't wanna hear about it.