Apple makes a device and sells that.
AND having more consumers means more available people for the developers to sell their product to.
Can't all be like Balmer "DEVELOPERS DEVELOPERS DEVELOPERS" for Microsoft, which traditionally isn't trying to sell hardware but just software for people to run on their hardware.
So having more software on their platform is necessary to sell more of their product (for Microsoft/Windows).
Marketing/selling products to developers, or enthusiasts in general, is a loosing strategy. They're a small niche that's too finicky and very difficult to please as every one of them expects different things tailored specifically to their own weird usecase that nobody else has, they have little brand loyalty and a high skillset meaning they're likely to drop you and port their shit to the competition or build their own self hosted alternative the moment you don't please them anymore. Not worth it if you're in the business of making shit tones of money.
Making products to please the Average Joe consumers is way more profitable. That's why most niche enthusiast brands end up either going bust, or making a deal with the devil and selling off to giant mega corps, or just emulating the giant mega corps, while abandoning the enthusiast userbase that made them popular. See OnePlus, Pebble, etc.