I love the way road tires wear down to a flat shape right before the rubber wears through to the casing. That flat spot tells you you've put in some time on the bike. You've covered ground that would really show up on the map. You've gone from point A to point B. Or more likely, from point A to point A many times.

The last few hundred miles before the wear finally breaks through are super-suspenseful. Kind of like waiting for a kidney stone to pass, but without the pain. And then one morning you're innocently getting the bike of the rack for a morning ride, and your fingers run over the rough of a torn blister in the tire:

And then you get to replace the tire with a nice, round, new one:

Then a quick pump up to 95 lbs, and you've gone from flat-top to round-top:

Continentals are great. They look euro-sophisticated, with the dark gumwalls that haven't changed since forever and the "Hand-Made in Germany" that you wish was true but you know probably isn't. They set onto the bead with a satisfying "pop." And the gator hardshells are almost flat-proof. It took a stray decking screw to puncture the last one that flatted out on me.

I hear grumbling from people like the Velominati that they "don't corner well," and blah blah blah. Listen: south-central Kansas is goat head country.

I'm not going out there with some lightweight, flimsy-ass tire or (gasp) tubulars just so I can walk my bike home. 

And you feel like you've really extracted your money's worth when you throw the old tire away, or recycle it, or turn it into a monkey habitat.

I don't think you get this kind of satisfaction with many other sports. You can't really wait for running shoes to wear out like this without putting yourself at risk of injury. Ditto tires on motorcycles or gas-powered wheelchairs. (though to be fair, if I lived somewhere with hills or technical roads, I wouldn't run my tires as long as I do)