This discussion might be beneficial to those following along here. I do vow to keep our discussion civil.
You’re asking why doing a squat or a deadlift is beneficial to the average person, yes? Because strength matters – in golf and in life. By lifting, you are learning how to produce force.
Squatting is a way to produce a lot of force against the ground. In an ideal world, we could use our hips to stand the weight up. We can’t put the bar on our hips, so we have to place it on our backs. The distance between the hips and the bar is the back, which means the back is helping to transmit force to the bar. As you train, your back gets stronger as a result. If you’re assuming the hamstrings are tight and pulling the lower back, wouldn’t you want your lower back to “pull” back?
Both the squat and the deadlift produce strong “core” muscles because in both movements, the midsection has to remain tight in order to most efficiently produce force.
Another benefit of training “big” movements is the fact that your body works as a system instead of each individual group working independently.