It's all about American culture, because this just isn't the case for women from other parts of the world at all.

In America, being an extremely LOUD, boorish, extroverted person is esteemed, and that's who white American women want to date and marry (regardless of whether they want kids or not, as many of them these days don't). Men with dogs fit into this stereotype well, whereas men with cats don't, they're stereotyped as "nerds" and introverts, and white American women have no interest in dating them.

Again, note that this is entirely cultural (subcultural?), and not universal, even within America. Immigrant women are usually not like this at all (which is part of why I only date non-American women these days), and also black American women aren't real keen on pets either.