Carol, that is due to the perception of wild blood, there is one of the US cat organisations that wont allow them to be shown due to it.
I love the look of Bengals, but know i would struggle with their energy levels (a neighbour has 2), so I wont have one, but sadly a lot of people get them regardless and then struggle - you also have the issue that people try and make money off tabbies due to calling them Bengals, I have seen people on forums be told what they have just bought isn't really a Bengal at all, and I suspect a lot of newspaper ads are tabbies.