Having a hardware, and thus an ecosystem, is more than making (more) money. It's about controlling the business.
Being a console manufacturer not only nets you more money due to the cut they get in every sale, but also the influence they have over other developers. Not only that, but arguably your brand is associated with every single game that runs in that system, which in turn makes your company and your games more valuable, because the chance of people knowing the console manufacturer and not a random third party developer is higher.
And the one who has the keys to the kingdom is King. Why do you think Epic has an Store now and is pushing to compete against Steam? Or is going after Apple and Google to have their own App Store there? Selling a product is just one of many ways to make money and grow your company.
My (locked) thread about how difficulty should be a decision for the developers, not the gamers.
https://gamrconnect.vgchartz.com/thread.php?id=241866&page=1
