As someone who’s worked with the Marketing Dept. a lot in my prior role, the reason e-commerce sites (and possibly Reddit) do the things you mentioned is because they’re overly focused on new user/customer acquisition vs keeping current customers/users who know the the products’ value happy.

There’s almost always a bit of political drama behind the decision too: Marketing gets to say that they’re acquiring new users in short term (thereby increasing their budget and clout in the Org) while destroying customer value in the long run