Not a good example. A car horn is intended to be a safety device. A reclining seat is intended to be a comfort device. You blow your car horn when you need to warn other drivers or pedestrians. You recline your seat when you want to be comfortable.

While we're on the subject of what things get used for, tray tables weren't originally, intended to be desks, notwithstanding the fact that they're certainly used that way now. They were intended to be a place to put your meal tray (hence the name "tray table"). That's one of the reasons why I think it should be compulsory to unrecline during meal services, as the tight seat pitch interferes with its use for that purpose. However, the rest of the time? It's the recliner's call, absent a compelling reason for not reclining, e.g. "you'll break my kneecaps," "i'm in a cast," etc.

I'm also curious -- what airlines have coach seats that recline so much that the person in front's head winds up in the person in back's lap? I've certainly never flown on such an airline, and I've flown all the majors.