When I drove my old dented, moss growing on it, Fiesta (mobile allotment shed) I used to get tail-gated a lot even when I was driving fast.
One day I hired a Transit van to take some furniture to my sister. I drove between Oxford and Aylesbury slower than normal because I was unused to the vehicle but nobody tail-gaited me or appeared impatient behind me. I came to the conclusion that drivers behind me assumed it was a man driving a van and, naturally (!) men are better drivers than women so if I was going slowly there was a good reason for it, whereas only a stupid woman would drive an old Fiesta and, whatever speed she was doing was going to be too slow.
One tail-gater annoyed me so much (in a 30mph zone where I was doing 30) that when he followed me into a shop car park, I told him he had been too close and that's why I had slowed down. He was annoyed but, to his credit, did come and apologise to me after he came out of the shop. I think he'd seen the baby seat in my car and had actually realised that he had been driving like a git.