I see your point and agree that vertical integration is harmful. I would like to offer the automotive industry as an interesting comparison of an industry with similar compatability issues.

All of the major components produced by the big manufacturers tend to be incompatible (without heavy engineering effort). When parts on a car are compatible between many makes and models it tends to be a third party parts manufacturer that has made it but a concerted effort from the big manufacturer that allowed that to happen. Think brake pads, tires, air filters, spark plugs. In most cases engines, their computers, interiors, transmissions and so on, are all make specific and also usually model specific.

No one is compelling BMW to make sure their engine fits into a Jeep. When I buy a BMW I am locked into their infrastructure and without their parts and support I could find myself without a working vehicle.

While you can often mix and match manufacturers parts so long as you can wield a few tools and have time and knowhow, it's pretty rare that someone wants to. Similar to emulators or jailbroken phones, IFTTT, APIs and integrations, it's easy to see there is a desire for this kind of flexibility but again it's often only a particular type of individual with a particular desire that makes it happen.

I feel that this desire for interoperability is niche. My mother on her Windows phone has been perfectly happy. I have never met anyone who wasn't in tech that has complained about interop. So while I agree it would probably be a good step to introduce more flexibility there, I don't think it's critical to protecting consumers against monopolistic behavior. If you buy an iPhone you are locked into Apple for that device, but you can still buy an Android. Just like I am locked into BMW while I own their car, but could still move to an Audi.