I love cameras. The modern digital camera is a wonderful thing. A highly optimised image processing computer coupled to an amazing sensor, wrapped up in ergonomics that make it nice to hold and use. It's a fantastically geeky chunk of tech that lets you create art.
But it's no use without a lens. And the lenses, to me, are where a lot of that art comes from.
And in addition to that, lenses tend to last longer than cameras. A good digital camera will last you a few years. A ten year old camera could still be useful, but it's going to be getting pretty dated. A ten year old lens is fine. The autofocus might not be as good as a new model, but unless you need that speed, it could be perfectly good. I uses old lenses, from as far back as the 1960s, and while they wouldn't be technically good compared to modern lenses, they give images a style you can't get any other way.
So while you could see your camera as being quite a temporary thing, which you may love now, but you know you'll be replacing at some point; your lenses could be with you for life. At the moment, I love my Alpha 7 camera, but I'd love to upgrade, and it's likely I will in the next couple of years. But I wouldn't be at all surprising if I'm still using my current favourite lenses in another ten or twenty years' time.
You'd probably guess from that that I take good care of my lenses. Caps on both ends, safely in a padded camera bag at all times, that sort of thing. But no. I treat them surprisingly badly. I rarely use lens caps, and chuck lenses in my unpadded backpack to roll around with anything else that's in there. But they're quite tough things. These old lenses don't have any electronics inside, they're all brass and glass, and they can take a few knocks. The rear lens element is usually far enough back from the rear to not be at too much risk, and the front element is less critical to the image quality. I don't really recommend treating lenses that way, but I take the risk to keep things quick and easy to access.