https://www.wsj.com/articles/ugh-green-bubbles-apples-imessa...
Apple is good at social psychology through product design, and it's not hard to imagine them employing similar methods to single out non-App Store apps on the phone to make them seem suspect for being less official. Less technically-savvy users will shy away from third party apps and sideloading if Apple's UI makes those apps seem scary. Thus, this can be a means for Apple to allow additional freedom while deterring most users from pursuing it, minimizing their potential exposure to third party insecurity.
The costs of someone not participating in the “blue bubble ecosystem” are borne by all of the people trying to participate in the conversation. Unless the cost of my friend side loading an app is felt by me, the same stigma approach is unlikely to occur.
Ironically, Game Center could have been that exact thing for gaming on iOS, if only they hadn’t mostly killed it off already.
To some extent you can already see this on desktop, when MacOS warns you about programs from unidentified developers and so forth.
I don’t care for iMessage particularly but I do know when it’s blue bubbles I have a lot more capabilities.
I actually think Apple could find a way to navigate it. They already allow one prominent alternative choice on iOS: non-iMessage SMS. If Apple allowed third-party stores, I could see them using their product, UX, and branding mastery to create the equivalent of the blue-bubble and green-bubble dichotomy for App Store vs. 3rd party downloaded apps. Creating a social stigma without technical restrictions, so to speak. So allowing an alternative while at the same time encouraging users not to partake in it.