Because you are describing the informational construct known as discovery, which can - and is - provided through many methods in every field, including gaming, and does not require advertising whatsoever.

Minecraft is basically a cultural icon now, despite having no effective advertising throughout its growth years. It was only after it was already gargantuan that Minecraft Pocket Edition started seeing adverts, primarily because the parent company ran out of ideas of what to do with their money, which is often the motivator for a lot of advertising budgets.

Specific to the games industry, discovery is a problem if consumers both A. have no peer group involved in gaming to get recommendations from and B. have no sources of discovery media (ie, rankings, reviews, etc) to find games themselves. Which I'd definitely say is true - the two largest game stores in the world, Google Play and Steam, have incredibly bad discovery mechanisms built in, and the former's entire market is mostly an appeal to getting on top of said discovery mechanism through psychological manipulation in skinner boxes.