That is the value of strength training and strength training with free weights. That is what can be achieved with smart programming for the right person and consistent hard work. i'm not saying every one who lifts needs to actually doing this, but knowing you have the ability to do so if needed is a powerful feeling.
You don't get that from leg pressing.
It's a great feeling, isn't it? Even if a person doesn't reach their weight loss (or gain) goals, you've given them something useful that will improve the quality of their life for years to come.
Recently I had someone come to me for a consultation. 55 years old, 250+ pounds, can't take a flight of stairs. She's working with a trainer at another gym*, for half an hour at a time, with kettlebells. I asked her how much weight she was lifting, and I brought her a barbell of equivalent weights (25 pounds). I went through a mobility screen and once I was confident she could do a light weight deadlift variation, I put her through a few sets. She said she did the exercise with her other trainer with kettlebells, but that she preferred it with the barbell. I told her:
"listen, you might not lose as much weight with barbells as you would with a kettlebell. But if you follow my plan, in six weeks you'll be lifting three times that. In six months, you'll be lifting half your body weight. Now let me ask you this, if you don't lose the 125+ pounds you need to lose, what do you think will benefit you more, being able to lift a 25 pound kettlebell, or being able to lift half your body weight? Which one of these activities is going to help you get up the stairs, carry your groceries, and keep you out of a wheelchair?"
I don't have any particular bent against kettlebells, but when a person can't handle their bodyweight up a flight of stairs, they don't need to learn how to flail around with 25 pounds of resistance. They need the strength to be able to live their lives!_______________________
*I would never actively poach a client from another trainer. She sought me out after being dissatisfied with her results.