Apple especially. They've firewalled developers from developing meaningful extensions to iOS, threaten to sue anyone who researches their systems, and will die clutching their App Store revenue rather than defer to the user's choice.
Apple could easily be incentivized to improve the App Store and first-party software if they let developers compete with them. They don't, though. It's a deliberate, arbitrary decision made by a group of people who's primary motivation is to not disturb the profit margins. You can make of that what you will, but methinks their way of computing is due in for a reckoning. Someone had to blink.