It's kinda naive to suggest that people don't roleplay only because they can't have side characters.
I didn't say that, I said that prevalent use any and all RP info results in players that have characters up to nefarious activities hiding that from both character (sensible) and player (arguably not so sensible). I personally don't RP from side characters, though my own characters might speak to them from time to time. The feature as requested is of little personal use to me at all.
Don't see your point here, really. People who don't roleplay because they are afraid of being metagamed which might lead to their character "losing" are half-hearted roleplayers to begin with.
Of course there is always going to be a issue of metagaming, you know what though, there are differing levels of prevalence. When something occurs but is infrequent, people in general will role with it and take the risk. When something is so prevalent that you can pretty much guarantee the outcome, then no people aren't going to bother, they are either going to find a different story to tell, or they are going to decide that they will RP it in a different way. Remember not all RP is on coloured paper. And this is what we see, the problem here is the the RP is now through a limited set of actions, with a very limited audience, so that if the story reaches a successful outcome players, not characters, feel betrayed, and we have the very real issue of losing players, as has been demonstrated by several of the larger betrayals in the last few years.
You probably think people in RL are bland because they don't narrate their backgrounds and don't retell you their inner monologues.
The level and types of interaction, and ones ability to mask their emotional response in real life are completely different. They are of course different mediums that have different requirements, just as the story elements of a book and that of TV have different requirements and implementations. Besides which its RL, I'm not necessarily looking for an entertaining story from it.
If you are a backstabbing traitor of course you must keep it to yourself rather than warn every other player about upcoming devastating treachery and expect them to play along.
Again, you miss context. In real life you might think someone acts odd or shady. That would not entail that you automatically assume he is out to screw you and take actions to marginalise them. I'm not talking about using RP to necessarily warn people about exact plans, but in BM currently if your character is even the tinniest bit "disloyal" or shady, the general player base will take that as a reason to be paranoid about your actions.
