My family leaves me alone when I'm on a call, but feels free to interrupt if I'm quietly working. Sometimes, I enjoy the company, so I don't want to tell them to never do this, but I also sometimes need focus time. The sounds of a call provide an audible signal that This Is Don't Interrupt Dad Time.

In other words, for at least some people, it's not pretending to work so they can slack off, it's pretending to be in a meeting so they can actually work.

I imagine that in-office workers with disruptive coworkers might want to do something similar.

I can't say why they are avoiding work, but it sounds to me like they are ashamed of letting their family see them slacking.

Giant majority of people I know with kids wishes for some more alone time.

I believe they have kids