The crowds she draws are literally embarrassingly small and low energy. So they probably figure why waste the effort, energy, and money. Better to waste the money on advertisements.
A lot of her appearances are announced with only the name of the city, but no times or places. Then, after the fact, there will be local news stories about the event, with a hand picked audience - not the general public. A little bit of backroom coordinating with the biased press.
Millie Millennial’s on the ground reporting in Akron, Ohio
https://www.youtube.com/watch?v=OXD3BCEWDAU