this is a thing actually lol. Although the individual mandate sorta screwed it up for a few years

most commonly it's people near-ish to the northern or southern border going to canada or mexico for prescriptions, dental work, etc. There's also a lot of people travelling for surgeries that aren't covered by insurance and are ludicrously expensive and hard to get in the states, often things like hair transplants or trans top/bottom surgeries, but probably other things as well.

I mean shit people also order their medications from under-the-table overseas pharmacies pretty often.