Nice topic
I've gotten many comments over the years.
One is the girlfriend-question: "Why do they have to make such an infernal noise?" - I've tried to explain the wonders of fast-revving engines, but somehow it never really makes an impression. The solution is to always make sure the girlfriend has something interesting to do in another room, while I watch an important motorsport event on TV. Oh, by the way, the girlfriend does like to watch Valentino Rossi, as she sees him as a funny and modest character, completely unlike the macho types she gottoknow, when she lived in Itay for a couple of years.
Another is the family-question, often raised by my dad: "Why would you want to watch them drive round in a circle, nothing ever happens, in particular overtaking?" - I've had reasonable success in explaining the challenge of driving at the limit in testing circumstances, although some will ask why I don't watch rallying instead, but the lack of overtaking has often caused me to experience an F1 race as two hours of processional boredom. Explanations concerning aerodynamics as a hinderance to overtaking usually provoke a headshake and a sigh...
Then there are the friends who does follow racing occasionally - fourty years ago, they wanted to know, how good Tom Belsø really was, twenty years ago they wanted to know, if Jan Magnussen was going to be world champion, today they want to know how long it'll take for Kevin Magnussen to win his first world championship. Fourty years ago, I replied that Belsø was good enough to be in F1, but too old to develop into a GP winner, twenty years ago, I replied it depended on which team(s) he'd be signed to, today I reply that we'll have to wait and see.
And finally there are the politically interested friends: "Why do they race in countries that have no or little tradition for manufacturing cars, and from where no driver of real merit ever came? And why do they go to al these non-democratic nations - China, the Gulf States and now also Russia? And is it really true, that the head honcho agrees with Putin's views on homosexuality? What sort o planet do they live on?". To which I reply, "money rules", "money rules", "yes, but he's way beyond 80, so his views might be a bit out of date", and "the planet of money". All of which results in the follow-up question: "Then, why does an intelligentperson like you watch it?", to which my most succesful reply so far has been, "so I can keep updated on the identity of the sponsors, so I can avoid their products...."