Why does so much "fitness advice" consist of telling complete newbies or people who have dabbled in weightlifting to pick a program that has you lifting heavy weights and just do that? Why am I not seeing people recommending pull-ups, push-ups, bodyweights squats & lunges, and basic mobility work?

I'm asking out of curiosity as well as to gather opinions before committing to a heavy lifting program vs. a calisthenic-focused program.

Edit: Got enough helpful discussion on this thread so far. Thank you.