Plus just think of the sightlines. The furthest seat from the ice in an arena can barely make out details from that distance. Upper deck at a football stadium for a surface smaller than the size of the football field? You'd just be going for the vibes while disappointing your kids.
Plus you have to think about stuff like ambient air temperatures for the ice surface to not turn to slush in a stadium that size compared to an arena...or the need for an ice plant for more than just spectacle events. Temporary ice surfaces can be set up, of course, but they ain't cheap.
Concerts would be the thing that gets lost...but the acts that can fill a football stadium are the acts that already go to the football stadiums in summer.
Swift is going to Indy during the nfl season. But the number of acts that require an nfl stadium a few and far between.
Again how many non sporting events are held in Minny, Indy, Det from Oct to march Since you would t host those events outdoors during that time? Is it 5? 10? 15? That’s the revenue side of things.
Costs, in terms of wear and tear and maintenance, pure outdoor one will be more expensive to maintain (save for the retractable roof ones which honestly, not worth the extra cost to have imo).
Likely headed towards covered stadiums in the north. Hopefully they figure out how to have a grass field like LV/AZ or like Tottenham.