That's an interesting thought. One thing that comes to mind is that age-gating is often not a cut and dry boolean granting or denying access to an entire application. It's conceivable and even expected that a social media company may want to allow users of any age to access their platform but are legally required to age-gate a subset experience like adult content, gambling etc. I very much like the main street mental model for this, where we default to open access amidst a broad mix of establishments and scope age-gating as minimally as possible vs. having an "adults only" part of town.