Why can't the $29.99 unlimited option be offered to current customers?

I just transferred my service in September to Spectrum and find out that I clearly I should have waited, had I known of upcoming promotion. That is $15 extra that we are paying per line when new customers get the best deal. Seems like current customers aren't getting valued the same. I really like my service since switching, but I am really hung up on this snag. It's quite unfortunate, honestly. I feel current customers shouldn't be charged more for same service, doesn't quite sit well.