A small child climbing into an occupied lap does not first check whether the lap is available, or whether they have been good enough this week to qualify. The assumption is total, and nobody in the room finds it presumptuous.
Somewhere between then and now most people install a check. They begin auditing whether they have earned the phone call, the invitation, the affection. Birthright means the audit was never a requirement — and that the version of you who climbed in without asking was not naive, only unpractised at doubting.