You know, growing up we didn't have to lock our bikes. I remember leaving mine out without concern. And yet I can't imagine doing that today. Wild.

Anyhow, I lock my front for two reasons: my rear is nutted and my front is QR. It's QR secured by a hose clamp, but still QR. Who's to say which is easier to get off, a hose clamp or 15mm nut?

But secondly, I think stupid bike thiefs at this point have been conditioned to look at the front. If the front is locked to the frame most will move on.

Just my theory.