Chain lube is a pretty sacred to some people, and just one more thing to forget for others. I'm sure there are a lot of people who kind of fall in between as well. It's just the nature of the world.
Ideally you'd just be able to go ride until it was wore out, flat, or broken, like say a tire or that crankset that you never really liked but it came on the bike so you use it but hope it becomes 'broken'.
You can't really do that with parts like bearings and chains though, well you can, if you can stand the noise, expense, crappy shifting and that feeling as you pedal. That feeling that you just know it's going to skip and fart around back there the second you put any real power down.
The problem is that your chain unlike the bearings in your bottom bracket or hubs with their cute little rubber seals is exposed to everything. That's a tough environment for exposed moving parts to operate in let alone perform well without adequate lubrication.
But why the skeletal picture you ask? What possible bearing could this grim photo have when we're talking about drivetrains? I'm glad you asked, we came upon it last Sunday when we were out doing some pasture touring and it was cool, so I figured I'd share it with you. It's way more exciting than a worn out chain!