I could point out that country-specific laws may affect the ratings of games.
I'll use Undertale as an example, even though that game wasn't officially rated.
In the US, the game would likely get a Teen rating, especially with the violence on the Genocide route. (There's also the final boss of the Normal route.)
In Russia, however, the game would get whatever the 18+ rating is. Why? There is a lesbian couple in the game, as well as an encounter with two gay guards, and Russia has a law that makes it illegal to "promote homosexuality" to children, which I believe has been interpreted to disallow *any* positive representation of same-sex attraction. (I consider the Russian government, not the game's developer, to be at fault here.)
It's somewhat ironic that it is the Pacifist route that would make the game rated 18+ in Russia, when it's the Genocide route that is the most disturbing and would be responsible for the T rating in the US.
It's the same sort of reason that a small number of games here aren't available in Germany.