How do those recommenders find out about a product in the first place? Advertising and PR is how that happens unless a person happens to be friends with the owner.
Advertising facilitates discovery, reviews and recommendations facilitate sustained growth.
Apparently the average distance between any two Facebook users is less than 5, and that distance is presumably lower when you restrict to smaller localities like a country or city, so assuming that's a good measure of social connectedness, I'd expect news to travel fast if there's something interesting to say.
Somehow I doubt uBlock Origin or SponsorBlock run ads, for example, yet here we are all knowing about them, and allegedly somewhere around 1/3 of Internet users have an ad blocker.
Advertising facilitates discovery, reviews and recommendations facilitate sustained growth.