Also remember that Steam takes a 30% cut

20-30% cut, which is in-line with most digital storefronts.

which is totally unnecessary

Companies exist to make money. Making money will never be "unnecessary" for a company. And hosting secure data centers around the world delivering 15 Tbps a day is not exactly cheap.

and is what directly caused giants like Ubisoft and Rockstar to make their own storefronts.

Also remember that Ubisoft and Rockstar (and Microsoft and Blizzard) came crawling back to Steam all the same, meaning they thought they would make more money even with the 20-30% tax. So a 20-30% tax must seem pretty fair to these companies for what they are getting.