There's a somewhat worrying trend appearing in PC gaming in the last few years.
Just yesterday I was browsing the featured games on Steam's front page (on that scrollable area), and out of 14 featured games, six were either pre-purchase offers or early-access offers. In other words, almost half of them.
A pre-purchase offer means simply buying the game before it has been published. In other words, pay now, get the game when it comes out. Oftentimes (although in some cases not) there will be a very minor incentive to pre-purchase the game, such as a slightly reduced cost (eg. 45€ instead of 50€) or some extra content (which usually just means a few extra props that are rather inconsequential from a gameplay perspective.) In the worst cases you don't get any advantage at all for pre-purchasing.
Before the prevalence of Steam (and other such applications), ie. when basically all games were purchased as physical discs, there might have been a slight "advantage" in pre-purchasing the game if the game would be enormously popular: You were guaranteed to get a copy on publication day, often delivered directly to your home, while people going to the store may find it sold out for weeks. However, even back then this situations was exceedingly rare. With digital distribution even this theoretical advantage has been completely removed.
Pre-purchasing a game makes no sense. You are basically buying a game blindly, without knowing if it will be any good. You are committing your money on an unknown product, with no possibility of takebacks. That minor cost reduction which you might get will be of not much consolation if the game ends up being horrible. (Of course it will be even worse if the incentive is something else.)
Yet people keep doing it. They wouldn't make pre-purchase offers if nobody pre-purchases.
An early-access offer is basically an offer to get to beta-test different alpha and beta-versions of the game, for a fee. In other words, you give the game company money so that you can help them test their game. In a normal, sane world, this would be the other way around. But seemingly we don't live in a sane world, as people keep doing this. You get access to an unfinished product, you help the company iron out bugs... and rather than getting compensation for your work, you instead pay them money for it. (Of course you are not required to report any bugs, but you will still be playing an unfinished beta, and you will probably report problems anyway.)
The early-access business model has also another very real risk to it, from the point of view of the consumer: There have been actual cases where the early-access game has been pretty much abandoned by its developers. There are actual examples of such projects which had big plans, but only ended up implementing a small fraction of all planned features, and the final product (if it could even be called that) was a crippled, bare-bones version of the original vision that was promised to the buyers. By paying for early access, as a consumer you are actually taking the risk that you will never get the promised product (at least not in the form, or with all the features, that was promised.)
There's a Finnish saying that can be roughly translated as "it's not the person asking (for money) who's the idiot; it's the person giving it." People keep paying money to companies for unfinished or unreleased products...