[jandrese]

I think the answer is much simpler. In the US almost every home has a bathing/showering facility built in. There's not much need for a bathhouse. Because they weren't used by regular people very much, people got this idea that the only reason you would go to one is for some other reason.

In reality the total number of incidents of unsavory rendezvous in the bathhouses were probably not much higher than in countries with more extensive public bath house culture, but the percentage of patrons who went there for other reasons was considerably higher.

Basically without the normal activity masking it, the unsavory activity stood out.