What do you mean by “only”? You can really expect companies to behave irrationally. Pretty much every company funding Linux development do it because they expect this to benefit them somehow.
"I think Windows 8 is a catastrophe for everyone in the PC space. I think we’ll lose some of the top-tier PC/OEMs, who will exit the market. I think margins will be destroyed for a bunch of people. If that’s true, then it will be good to have alternatives to hedge against that eventuality." - Gabe Newell
Yeah, the existence of SteamOS, Steam Machines and eventually Proton were a hedge against Microsoft’s perceived shift into locked down distribution .
I think a lot of folk have a hard time reconciling that there may have been non-altruistic intentions behind something that is enjoyed today.
Similarly, Steam itself was a hedge against physical distribution to cut out the middleman. It wasn’t originally envisioned as a store for anyone but Valve.
But here we are today, and both have positive side effects that actually have outlived the original design.
They only do it because they are painfully aware their rent-seeking behavior is entirely at whims of ms/apple and they want to have some moat.