Virtual environments evince a significant lack of mainstream adoption. Relatively tiny percentages of the world population are involved in them in any way online. There's something clearly missing.
At the present time, virtual environments simply lack any compelling reason to exist that motivates mainstream users and might drive mainstream adoption. There's no killer app, or secret sauce that gets large numbers of people thinking "I want to get me some of that!"
Education? Limited at the moment, and educators are finding more effective uses away from the big services and in bijou environments like opensim. There's somewhere between 500 and 800 educational institutions operating in virtual environments at present, with presences ranging from active to inert. This isn't really representative though. If educators were representative of the mainstream, the world would be a very different place. More of us would be able to spell simple words than is currently the case, for example.
Sex? I'm not so sure. I spend a lot of time in virtual environments, and while there's certainly some sex going on, I'm more or less constantly surrounded by people who are egregiously and relentlessly not having any online. Still, as with any media or product, sex is one of the most effective mainstream killer apps, but still is only present in virtual environments in the form of (rather awkward) collaborative pornography.
Gaming? Blind people outnumber MMO gamers roughly 8 to 1, according to some (fairly crude) back-of-the-envelope math, and some numbers from the World Health Organization. That makes the blind minority larger than the set of MMOG players, right? Online gaming clearly isn't a compelling mainstream motivator at the present time, despite more than 50% of the population of developed nations being broadly categorized as gamers. Virtual environments are certainly central to most gaming, but they're just not bringing vast numbers of mainstream people online at this time.
You'd get far larger user numbers just supporting the blind community alone.
Essentially, virtual environments lack what is called "the killer app", that elusive and compelling reason for people to want to jump on board and start using. Something they want that they're willing to come after.
In that, virtual environments are not much different to any other product or service. They can certainly be successful (even wildly successful) with relatively microscopic percentages of the global population – unless they've hinged their business models on being impractically much larger – but they still don't have the secret sauce required to get the mainstream tastebuds salivating.
Art? Music? Tourism? People already get all of these routinely. Socializing? The average person usually exists at their socialization limit, unless you redefine socialization itself – as most social networks seem to do.
The closest thing most virtual environments seem to have to a killer app is privacy, and even that is a significant bone of contention these days, with privacy becoming a battleground of competing interests.
Without a compelling raison d'être for virtual environments, they (like the Web in its time, and the Internet before that) will remain a largely fringe item, until someone hits the right recipe for the secret sauce to make them broadly and ubiquitously delicious.
