I think the guy wants to know why not do bodyweight type of exercises, which have a low risk of injury, versus squatting and DL alot of weight, which do have quite a bit higher risk of injury, since we rarely ever have to squat or DL in real life or have to use that strength in real life activities, other than say sports? Moving a mouse and typing on a keyboard or watching tv don't require us to be able to squat 400 lbs.
My answer would be that doing the compound lifts allows you to move the most weight, which promotes overall strength and muscle growth. Compound lifts build a foundation of strength that makes it easier to then do other lifts (bodyweight stuff, curls, whatever). It's, in theory at least, more efficient because it's only 3 lifts a workout. I say in theory because once you add in assistance exercises, SMR, strethces, learning form, posting in this forum (you know how long it takes to find good gifs every day
) etc., then it does get a bit more time consuming than just doing lifts 3 lifts in 45 minutes 3 times a week, except for the blessed genetic few among us.
I would say try it and you'll see quote a difference versus just bodyweight stuff. Besides, DLing just feels bad ass compared to doing a pushup. That alone is worth the pain and suffering.