It is _100% true_ that people buy games, not engines.
It's also _100% true_ that companies that make tech that has no direct use case -- an engine for which there's no game that the engine was designed for -- make shitty, hard to use tech that do some irrelevant things very well (e.g. photo-realistic screenshots) and do relevant things very poorly (e.g. facilitating extremely rapid iteration on innovative game design concepts). This is why Unity sucked dick until around version 3 after EA started pumping money into Unity and telling them all the various things they had to massively fix in order to make the damn thing usable for real games. Likewise, it's why there is no single other successful engine in the market that wasn't original a custom engine for a specific game that was then "genericized" and marketed later, e.g. idTech 3, Unreal, Source, etc.
There is a famous blog article that we basically direct every last single indie, hobbyist, and upcoming AAA game developer to on this topic: [ur=http://scientificninja.com/blog/write-games-not-engines]Write Games, Not Engines[/url]. Gist of it is that writing technology for technology's sake without an actual game to drive the technology choices made just makes for shitty unusable engines.
And hence, if Unigine is just a pile of tech with no actual games being developed by the people making the engine, it's going to be an unusable mess for many many years until Unigine customers slowly push the company into fixing all of the mistakes they will be making out of lack of game-development experience and lack of viable battle-tested use cases. Which _may_ (I don't know) be the reason that nobody is using the thing; possibly everyone who's jumped through the hoops to evaluate it have found it to be just another Unreal wannabe that doesn't fix or improve upon all the many weaknesses of Unreal and, given the massive retraining of both developers and content creators that switching from from one engine to another entails, that makes it an extremely bad proposition for a AAA games industry that's dominated by Unreal. (The other possible reasons that Unigine is practically unused are their piss-poor marketing, pre-indie-explosion pricing model, complete lack of readily available documentation for evaluation purposes, and having no published commercially successful AAA games to prove that the engine is actually usable in the $200,000,000 budget AAA space that they seem to be targeting.)
Of course I have zero experience with Unigine, so I don't know what its actual failings are or what its actual strengths are. It could have been developed by people with decades of game experience who know exactly what is needed. My own experience with so many similar efforts indicates that it's the same crap we've seen over and over -- lots of very technically exceptional people spinning their wheels in the mud because they're utterly failing to understand that the game industry produces games, not technology.
IMO the biggest problem hindering any kind of widespread Unigine adoption is that it is so damn expensive.
When you drive, you drive a car, not an engine, but there is no driving without engine. What is the fucking point again? What are we even arguing about?
Some of the comments do not make any sense. The game engine gives developers a platform to create video games off of. For major professional gaming developers, the cost of the software is in actuality not expensive. Why waste time creating something entirely from scratch? When instead you can build off a solid platform saving both time and money. Developers do not work for free. The longer a new title is delayed from release, the lower the profit margin is expected to be and the more it will cost them to create it. Large mega-millionaire companies like that of Activision can easily afford to delay their releases. People looking from an eyeglass in have no idea what effort goes behind creating the titles people love. :p