Why are people willing to keep themselves up in one way, but not another (Details will help)?

I don’t hesitate to spend time on my hair, makeup, skin, etc., but can’t seem to exercise consistently.
Why does this happen?
People will go get haircuts, and skin treatments. We’ll brush our teeth, wear presentable clothing, and make sure we smell nice. We’ll do all of this in an attempt to look our best, but (some able-bodied) people won’t exercise. Why? It seems like a waste to me.