I think you're making the assumption that socio-economic status is the only variable.
There is also the "I have Apple, I'm creative". "I have Apple, I'm cooler than Android".
I don't know if the blue/green bubble thing is about socioeconomic differences, or if it's just about "you're not as good as I am".
If you're so sure Apple doesn't have a status feature, then what's the whole green/blue bubble about?
There is also alot of insecurity on the other side that is oddly enough projected on Apple users: “They must be using that as a status symbol or they are trying to look creative!” It’s always been like that really, Apple tends to fire up its own opposition. In reality Apple stuff are just workhorses now, and many of us just have an aversion to PCs that fall apart after a few months, or phones that kind of work but not really well, or tablets that double as space heaters…Apple is just the safe choice these days, the choice of cowards like me.
They say it’s to distinguish SMS from iMessage as if anyone would possibly care.
I care, as iMessage offers better quality photos/videos than MMS.
Also, international MMS costs money, while iMessage is free regardless of location.