It's one of the most stupidly bizarre things Ubisoft has done in recent times, assuming there's no deal with Epic preventing them launching day 1 simultaneously.
If you don't want to pay 30% to Valve, and circumvent it via alternatives, fine. But what's the alternative to the massive storefront like Steam, it's installed based and features? Certainly not EGS, even if they offer to take under 10% margins.
Now when you launch this and a host of other of your (then) back catalogue of games released this year and last year, in say 2025, on steam like you recently did with your old games, they're not gonna move much as they do at launch, and the cycle repeats itself.
Just a waste of resources, money left on the table, fragmenting the potential target audience and eventually they lose interest and the sale.
One of the worst marketing decisions they've taken in recent times, and they're reaping what they've sowed with this game, despite being really really good as the press and the players themselves day, it hasn't even done decent numbers on PC.