I've worked at truck weight stations.

On multiple occasions we've had truckers come in to get their ticket for overweight trucks, and I've had to leave the room due to the smell.

We're not talking about, "Oh, I forgot to put on deodorant" or "we need to spray air freshener when they leave". It was "If I stay in here I'm going to start gagging".

Painting with a broad brush is bad. The vast majority of truckers were perfectly kind, clean, great people. But I don't think there is any demographic that I've interacted with that has had a higher percentage of offensive smells coming from them. So while I strongly disagree with the "No Truckers" rule, I can understand where the motivation could come from.