There is some argument to be made that the cost benefit analysis for your average user doesn't make sense unless the platform is a significant improvement over steam. Having two fragmented systems is a huge inconvenience to users now almost to the point that I will outright refuse to play games that are not on Steam.
And for companies that shoehorn really bad launchers as an extra layer on steam like EA, you are doing the work of the devil himself
Some extremely popular games, like all the Hoyoverse stuff (Genshin/ZZZ/etc) or most of Blizzard's games, have their own launchers and aren't on Steam. So gamers are certainly willing to use non-Steam platforms and launchers if there's a reason.
That didn't stop overwatch 2 from eventually making its way over to Steam. They also have the best integration, once your steam account is linked to your Battle.NET account you don't have to even think about the launcher
And for companies that shoehorn really bad launchers as an extra layer on steam like EA, you are doing the work of the devil himself