If you’re not a billionaire and against this, you’re pretty much a moron and if you’re thinking one day you’ll be a billionaire, you won’t be based on your thought process alone.
There’s no sensible reason why anyone should have no resistance accumulating that much wealth to themselves. It isn’t infinite money for everyone, essentially you’re taking it from others. Yes, some fools kind of deserve or are themselves at blame for parting from their own money, but if there are no stops, it doesn’t motivate others from making sure they create methods to keep doing this to others. All to gain, nothing to lose.
Ads are not the only reason, but if you’re still on reddit, you clearly missed the point why reddit became popular.