As an aside, as a single person I feel the discounts that come with family plans to be weirdly discriminatory. I go with prepaid TMobile (10gb for $40) because it’s much cheaper than a regular(?) plan with only 1 line. But to hook my Apple Watch up to cellular, I need the regular plan ($75 for one line + $10 for Apple Watch) as prepaid tech is years behind and second tier (most MVNOs included). That means that the only way I can use an Apple Watch on cellular as a single person is by paying $45 more per month. Complaining about an Apple Watch is a first world problem, but I think the pricing system is unfair.

I really wonder whether young members of the family consume more or less data, or what other reason could be used to justify family-discounting.. but it’s probably like a parent comment said: there’s no correlation between costs to the carrier and price the consumer pays; the single/family split exists to create the maximum profit off both groups by penalizing single people and convincing families to add all younger members to the plan (even those that might not need it). IMO carriers should give an age discount for under 18, not a per-line reduction the more members are in your plan.