I’m from the US as well, and I can verify that very few average people use those types of messengers primarily. It is almost exclusively iMessage and SMS/MMS/RCS texts as the main form of messaging. I will admit that quite a few people will use the messaging features that are built into social media apps (like messaging in Snapchat, Facebook Messenger, etc). At least to me, it seems like those are moreso used for sending memes or messaging people you don’t interact with regularly and are still secondary to the other forms of messaging.
You’re correct on the two thoughts you listed. Wishlisting also makes the game more visible before release. For example, highly wishlisted games appear in the “Popular Upcoming” section, along with some other spots. This increased visibility before launch then feeds into the two points you made. I believe games that are highly wishlisted before launch are also more likely to appear on the frontpage right after launch.