I think it's mostly because the run would be boring to optimise and watch, so there's little interest in competing for it, although there have been a lot of questions about this so they may be considering adding it but I wouldn't know. I'm not against it but I definitely wouldn't run it.
Sorry for not being that active lately, I'll try to get more active now!
To answer the question: It's pretty much what Circinus said. Once you beat all matches while only scoring a single point (since any more would waste time) you essentially already got the perfect time, there's not much you could do after that. While not really an alternative, Sports Mix All Cups has Hockey in it (with all others together).
I wish there were ILS BUT THERE ARENT ALL JUST BECAUSE MARIO ODYSSEY RUNNERS ARE TO GOOD TO KEEP UP WITH ALL OF IT
