Nothing is making anyone purchase anything Apple makes. Only those that have chosen to do so are spending on Apple products. No one is locked in. Photos, documents, texts, and music can be moved over to any other handset manufacturer. Apps can be resubscribed to on another platform. You can move about the cabin as you like. This myth needs to stop.They want to sell iPhones and lock you into their ecosystem. Yes it would be nice to sell 10x (just an example) more AirPods but these smaller/cheaper products are to push you to Apple.
Let's not forget Apple is also a fashion/brand company. If you want to be seen wearing Airpod's/Apple Watch then you need an iPhone. Or maybe you're looking for a TV box so pick up an Apple TV and start building a library on that. When you see someone wearing Airpods you'd think "they have an iPhone". It's there to almost subconsciously let you know what product they have. If you are in a room and 8/10 people are using their iPhone that looks good for Apple. Airpods is an extension of that.
Once they get their hook in you then it makes it harder for you to leave once you've invested in them.
Opening up their products to work with Android/Windows means they have less of control over you.
When I first got my iPhone 12 five years ago I had Sony earphones. They worked perfectly fine and sounded great but the experience was clunky and I needed an app. Eventually I got Airpods because they "just work" with iOS.
When I was wanting to upgrade my phone I considered going back to Android and I could've but I decided not to because I can't live without my Apple Watch. Yeah, Android has smart watches but I don't think they're as good as Apple Watch and anyway I had built up ~5 years worth of purchases in Apple's ecosystem so didn't want to start over again in Google's ecosystem.
Maybe some people feel the same about Airpods. They'd leave iPhone but they know they'd not get the same experience on Android with them. Opening up Airpods to Android means people would be less likely to stay with iPhone when upgrade time comes.
Apple makes products that work "better" with other Apple products. It's just what any decent business would do if they made multiple products that can work well together. Are we getting on Google for its earbuds, or Sony for its headphones and their mobile phones? Google makes watches, Apple makes watches. I'm sure the Google watch will work better with a Google phone than an iPhone. It's not the end of the world if it does.