That may be your experience, my partner and I use it co-op on every game that has it and watch each other play singleplayer, so it’s almost never out of the dock. I imagine many families with multiple kids and not enough budget to get everyone their own would do the same.
Given the context of the article, the alternative suggestion isn’t “set up your own server” but “use software that doesn’t require a server”, which sidesteps most of that list.