If you leave you car sitting in the driveway, as I have to do due to no garage, ham plates are advertising to the whole neighborhood that you are a ham, especially if the plates say "Ham Radio" or "Amateur Radio" like they do in Oklahoma and Texas. Such statements weren't on the plates in Iowa.
So now the neighbors all know you are a ham radio operator. Guess whose front door with be getting the knocks (and accusations) whenever someones TV or internet has issues.
73 JOhn AF5CC
I live at the very end of my neighborhood (cul-de-sac), so I have to go past every house and see every vehicle, on the way to my house. Some of the neighbors have 3 or 4 cars, so they don't all fit in the garage. I can't even remember if any of them even have plates on their car, let alone a ham call sign. The only time I ever read license plates is when I am sitting in traffic.
The dead giveaway for me might be the 43' vertical that everyone in the neighborhood can see. It's been there almost 3 years now. A few have asked me about it, but no interference complaints.
I live in Michigan now, but when I lived in Arizona, I had a 50' crank-up tower with a Tri-Band Yagi. No one even seemed to notice it was there and never had any interference complaints. And, I had vanity plates with my call sign on them.
I doubt that any of the neighbors have any idea what Amateur Radio is. When I tried to explain it to the neighbor behind me, they wanted to know what channel I was on, so they could listen to my radio show. I just told them "it's not that kind of radio".