If we think back to the beginning mobile messaging, the first thing that comes to mind is Blackberry and the Blackberry Messanger (BBM). In a world of SMS, the read recipts and primative smiley faces BBM afforded its users was unique. So unique infact, that RIM was convinced that this "feature" of their devices was so compelling, there was no reason to ever let it be outside of the "Blackberry ecosystem". At a time when iPhone's and other capable smart-devices came to rise, it seemed customers weren't swayed. Mind you disregarding RIM's other shortcomings, it would seem in hindsight that keeping BBM internal was a mistake.
Evidence of this mistake? Back in 2010, a former intern of RIM went on to create Kik after having spent a summer working with the BBM team and wanted to create a "BBM-like app that worked on all smartphones"  In fact, he even went as far as to offer to discontinue his work on Kik if Blackberry made BBM cross-platform. As history tells us, Blackberry said no.
Fast-forward to today, and we live in a generation where communicating with a "green bubble" might as well be akin to carrying to a Jitterbug phone. Why are iPhone-owners so ambivilent towards their non-Apple-weilding friends? I won't speculate (I use a OnePlus 5 myself), but as I thought through this situation, there are some key decisions Apple conciously made:
- You may recall prior to iMessage being introduced, all chat bubbles were green on iPhone. When iMessage hit the scene, Apple opted for a more pleasing blue color for those messages. Oh how easy it now becomes to relate the green color to old.
- iMessage came to fruition in a period where "unlimited texting" wasn't near as ubiquitous as it is today. Positioning iPhone's as having "free and unlimited" texting was attractive to a market who used to pay for texts in blocks of 200.
- Apple ecosystem has always been closed. Even after the App Store was released, you couldn't change the default SMS/ texting/ messaging app even if you wanted to. It was irrelevant if there were better apps - you simply couldn't use them.
- Apple integrated iMessage (internet-based messaging) directly into SMS (cell-based messaging) in a mostly-seemless transition in which no one had to opt in to start using. What's the best way to push adoption? Don't make it a choice.
- In a continuation of that point, I'd venture that many "casual" users don't know the difference between cell-based SMS, and data-based iMessage. iMessage might as well be a less powerful GroupMe, Hangouts, Whatsapp, etc.
- And on top of all of this, Apple made it difficult to leave. So much so, they got sued for it.
So why is it that these many years later, Apple's iMessage is a point of contention for most as why they want to stick with iPhone?
The short answer: it's tough to leave an ecosystem. As someone in technology, I find that many carry iPhone's primarily for the "ease of use" that comes with communicating with friends and family via iMessage. Undoubtly by design, had Apple not limited the choices for third-party messaging apps, the "pre-installed" iMessage would be just another app in a sea of choice. Instead it's the defacto reason iPhone's continue to fly off the shelf. It seems to me that "Think Differently" doesn't really apply anymore.
I'll leave with one thought - if you're in the Apple ecosystem, what's keeps you there? How many Apple services do you really use? Does the benefit of one (or a few) outweigh the shortcomings of the many? Not all companies have closed ecosystems, but Apple (and maybe Bose) are the gold standard for them.