Depends on what you mean by 'mainstream' as well as 'inconvient' - for whom?
do exist and continue to be used but you'll have to be clairvoyant to know any secrets governments are hiding from the public, scandal-hungry media, and whistleblowers from among their own midst. Either those clairvoyants actually don't have a clue, or they're unable to find a platform for their correct predictions. My impression is they're wrong every time - whenever something of truly global import happens, it mostly comes out of left field and as a total surprise to those 'seers' dabbling in prophesy; previously inconspicuous individuals are suddenly discovered to be monsters whom not even the most paranoid conspiracy theorists suspected of any wrongdoing before, wars break out in the unlikeliest of places, seemingly robust companies go spectacularly bust, all without savvy clairvoyants raising any alarm beforehand.
In my opinion, the public in general and occultist in particular have an voyeuristic appetite for anything allegedly 'secret' and 'hidden'. In addition, conspiracy theorists like their inconvenient secrets juicy - actual conspiracies like the
are too boring for them (who gives a shit about lightbulbs anyway?), shady real-estate deals not sexy enough, bribery too mundane. There always have to be centuries-old secret societies or at least Satanism involved, government cover-ups (unfailingly effective, in the way that all governments are), blood-curdling tales of human sacrifice or whatnot, hidden manuscripts, secret symbols on medieval churches, the whole Dan Brown shtick. Add the usual suspects (e.g. Freemasons), some super-secret technology that apparently explains absolutely anything, and you're ready to join the other barkers up the wrong tree while in real life illicit arms deals continue to go down, or laws with generous exceptions for Big Business are being enacted.
I think that conspiracy theorists aren't interested in making the world a better place by unveiling 'secrets', they're solely in it for their own titillation. If something was genuinely secret, you and me wouldn't even know that it existed (and those clairvoyants wouldn't even know in which direction to look). It's always global big picture, with one single (occult) organisation behind it that never suffers from infighting or power struggles, never commits blunders, implements its nefarious agenda without a single hitch and is always in perfect control of the governments of all 193 UN member countries; it's never just special interests of a few companies or dictators. Lobbyism? Too dull. Industrial espionage? Ditto. Maybe conspiracies are the biggest psyop of all, a new opium for the masses.