It's not a simple cost/profit thing though, it's a complete restructuring of your entire way of selling. To go in all the way, it also requires the knowledge that giving away your game practically for free doesn't necessarily mean less sales, especially if you're also selling on PC. Hindsight is everything on that one and I'm not sure that's something even MS foresaw when they started all this.
You think if Sony couldn't sell millions of copies of Ghost of Tsushima, plus get millions more players paying subscriptions and, potentially, buying DLC, they wouldn't do it?
But it'd require day one releases on PC, it'd require the risk of it not working and it'd require a huge amount of amount of money to get set up.
That doesn't mean Sony aren't going to end up the same way, it's just the reason they didn't do it first. Like I say, hindsight is everything.