> Do movie theaters let kids under 18 into an R rated movie without ID?

I mean, yes? At least in the Netherlands they do, I just went to see new the Jackass movie last week and half the theater was kids without parents present.

Also this is a bad comparison because a theater (or bar or whatever other venue checks IDs) doesn't store those IDs forever in perpetuity, and they definitely don't share it with one of their 9000 "legitimate interest" partners who do lord knows what with the IDs.