I did a podcast about a year ago with Kyle Hunt - in this podcast we talk about a number of things but one thing that stood out was a 4:00 snippet about why we train. You've seen the "Why Train?" wall sign; now you can see the video.
If you don't have time to watch this, in short: because we are animals. Men are being declawed and our teeth are getting dull. Our bodies and minds were never meant to spend half of our day laying around and the other half on our knees. Training is one of the many ways we can challenge ourselves both physically and mentally. So put the damn bar on your back, push the sled around and put some pressure on your body and mind.
You can listen to the entire podcast here: