Heya,
Actually, it has nothing to do with what the devs give out. If that were the case, nearly every game would be considered near crap. Sure, sometimes, a `demo' or show off can be really exciting. But really, it's incomplete, so no verdict, not even "it's good!" should be given.
The real reason you don't see professional reviews that say this game is awful, save your money is because that's NOT good business for anyone. A big site slamming a new game will get a lot of negative feedback from people who are interested in selling that game and games related to it. These big review sites don't make money enough to just do things like this; they survive a lot by basically getting free stuff, reviewing it, and then giving it back (unless some places gives them software for free). Usually there's some kind of exchange or contract here. A company that makes a game and hands it out to reviewers only to get slammed and the readers told it's garbage isn't going to be handing their game back out to reviewers again, as it will no doubt hurt sales. Think about it.
These games are not exactly crap though. You have to understand that people tend to go black & white when it comes to games. You either really like it, or really hate it, it seems, when it comes to telling people if it's worth playing/buying. Really, all games are `playable.' But obviously not the same talent goes into every game. And we tend to put various titles high up and compare everything to them in the sense that they come close, are similar or simply can't match it and thus are crap.
So again... how do you make money by telling everyone that near everything is basically not worth their money? Because seriously, how many good games, according to us who play them, actually come out each year?
The other problem is scaling. Why have a scale of 1 to 10, when everyhing, literally everything, always scores at least a 7 out of 10? How many 4's are there? These are the games that just are crap and manage to actually turn on. 5's would be average on a scale of 1 to 10, meaning, nothing special but not horrible. According to all review sites that use that 1 to 10 scale, everything is above average. EVERYTHING IS ABOVE AVERAGE on these scales. EVERYTHING. And it's completely stupid.
Adjust the scale to 1 to 5 for example, and 2 stars would be average, 3 would be just over average. We should see a lot of 2's and 3's out there. A few 4's and maybe one or two 5's a year.
Alas, in my opinion, the only reviews worth actually taking serious are reviews that don't use scales but rather just tell you how the game worked out, bad or good. How often do you find reviews like this? Yea, like, hardly ever.
Very best,