Why lift?

The question, "why lift?" is answered by doing it seriously for 6 months or so. Strength is like education, you don't realise its importance until you have it, and people who are too lazy to get it will come up with all sorts of elaborate arguments about why it doesn't matter to them. 

• "But I don't want to bulk up." I'd believe this woman if I saw her smashing herself with cardio, but she's walking on the treadmill at 4km an hour reading Woman's Day. She's just lazy. 
• "I get enough leg work playing soccer." I'd believe this guy if he were going hard on upper-body, but he's half-benching 60kg and doing one million curls with layback. He's lazy. 
• "I just need to work on my core." This person isn't doing three minute planks, either. The purpose of your "core" (which we used to call "the waist" before it got trendy) is to keep you upright. Is it harder to stay upright with a big-arsed weight on your back? Then you are working your "core" while squatting. They're lazy. 
• "I have a bad back, and bad knees." This is why you must lift, just starting easier and progressing more slowly than someone with no problems. That you don't do it means you're lazy. 

Cardio is important for good health, beyond a certain level it's not helpful. I know many people who ran for many years, and looking back said it was a waste of time. I know nobody was has lifted for many years and said it was a waste of time.

This is the difficult part about selling training, whether by "selling" we mean signing people up for PT, or simply getting someone to train themselves: you don't realise its true value until you've done it for several weeks at least. You lift because lazy is useless, and stronger is better.