IANAL. It's not about cookies per se, it's about your information and what it's used for. If your information (e.g. a unique ID) is used for something you want (e.g. login), that's fine. If they want to use your information (could be the very same information, i.e. your unique ID / user profile) to track you, advertise to you, sell your profile to advertisers, ... they need extra consent for that.
