I'm actually surprised that this isn't how it works at Trump rallies considering he is a former president. When I went to see Obama at the Lincoln National Cemetery, they had everyone arrive in a different location and then had them go through security before getting on busses to the real location where his speech would be. I'm assuming that's what is happening for Kamala's rallies as she is the current VP. But it also just makes sense from a security standpoint of a former president? I'm also no expert and just speculating.