Again, should they do it? Yeah, but it isn’t hindering gamers. Your example of a family playing fortnite all on different devices that want to play together is a pipe dream. At the most youd have 2 possibly a farfetched 3 people in a household that want to play together, and i seriously doubt they’d really be hurt by not being able to play with each other in an online game with up to 100 other people. Also why is sony the only one singled out on this when switch dropped crossplay for fortnite recently.
In the real world this does not negatively affect but a very VERY small portion of people, and its only a minor negative, not a game breaker in the least. So can we please stop acting like this is somehow grinding everyones gaming fun to a hault?