Subs protect games from bots and “buy gold now” spam, though not entirely. Having a bot account banned now means nothing as it costs nothing to create a new one and just try again. This is why most games with a trial feature or free to play element restrict the players from communicating, trading or pretty much anything that can influence a subscribing player. Problem is even if you keep banning the cheating alphas they’re still making more than they’re losing and thus winning.
I hate how most games now are veerying away from subscriptions, it was the best to pay and be on equal footing with anyone else who paid the usually minimal fee.