Because her signal can and would be traced back to her physical antenna. FCC has roving "compliance" vehicles that monitor and remind HAMs to start and end their broadcast sessions with their license ID, among other things.
HAMs don't want that "late night knock" on the door so they include their ID.
Not the real thing, but you get the idea...
(At least, that's how it was for my neighbor in the 1970s)
I've heard of those roving vehicles since I got my license but in rural Texas they weren't a thing. Only know one HAM who retired down here from the Pentagon who had stories of them. That said, we've always been self policing. And since we mostly do storm chasing, emergency stuff and public service communications we go extra miles to help interested parties get licenses and be involved. We are starved for man power. We have a few guys in our group who've tracked unlicensed users themselves and gotten them set straight, either licenses or off the radio.