is PbP done as a main stream medium?
I think I see one of these threads at least once a year...
The answer is yes and no, depending on who you ask. But, more directly, radio didn't die with MTV starting up in the 80s, despite many predicting that would happen. The rise of Amazon still hasn't resulted in the demise of brick-and-mortar outlets. Despite their best efforts, streaming services haven't killed off movie theaters. Neither did home video, decades earlier...
And while there are other options for role-playing online...newer, fancier, shinier...they still don't function in the same way RPOL does, which means that a significant percentage of RPOL users aren't interested in them, for a variety of reasons (several of which have already been listed.)
New technology and new applications of existing technology keep coming along. Every few years, there's a hue and cry about how this latest development is going to be the demise of some other tech/application/whatever...and while it invariably has a significant impact on the older one, rarely does it actually succeed in killing it altogether. I mean, the closest thing I can think of is cell phones...but we still have landlines in place. You can even, on rare occasions, stumble across a payphone.
If I had a dollar for every time I heard someone ask if some form of tech/lifestyle/etc was dying or dead, only for it to last years or even decades beyond that question, I would have been able to buy a house a long time ago, rather than still renting...