Because it doesn’t seem to matter currently if you play ranked games or casual games, the general experience tends to be the same. But one has numbers and things to go with it. You still get people playing to win in casual games and you get people dicking around having fun in ranked games, and the ranks don’t necessarily indicate how they play as a team and a whole bunch of other things that make it less than ideal.
MTG Arena - there’s a regular play queue and a ranked queue, and people definitely play to mess around and try new decks for fun. This of course doesn’t cease to induce salt from sweaty gamers in the play queue.
Even ignoring games that you consider “in the gray area,” who are you to say someone can’t find a way to have fun in a game that doesn’t align with your way of having fun? Not everyone is playing the game hoping to land on an esports team.
Edit: I’m mostly referring to casual queues - ranked queues being hyper competitive does make sense. I’ve just seen the same argument made that casual queues should be the same level of competitive.