You could say there is a contradiction in marketing between having a large list and having a useful list. Every marketing department wants a list that is both large and useful, but the larger the list is the less useful because it's like trying to sell bras to men. They can't have both without weakening the list overall, but they need both to grow.

Every marketing team trends towards decay as the contradictions rise, until eventually they all become worthless spam.

I'm gonna assume most companies aren't ran by people who'd take this sort of holistic view of things and instead if KPI go down the head of marketing gets fired or whatever. I mean fuck marketing departments but I assume even they're like "incessantly mailing bra ads to people who try to unsubscribe probably doesn't win us any favours with anyone"