More entrenching of their services as a monopoly. Without a doubt the cost of a sales page and servers would be less than 30% of a lot of games sales. It’s a cost they are willing to pay if it means keeping their walled garden and 30% flat rate. (Like Sony selling consoles at a loss)

Any open source Linux contributions from steam (proton) are welcome because it’s not tied into their monopoly and people can use them freely.

You can enjoy the small victories while also being aware of future outcomes from these corporate giants.