Think they were found to be carcinogenics or harmful in some other way.

According to the Wikipedia page, there was a potential issue with male fertility. It seems to me to be a better-safe-than-sorry situation.

A 2003 “paper reports the first epidemiological study designed to investigate the possibility of a relationship between cyclamate and cyclohexylamine and male fertility in humans.” It states that “the results demonstrate no effect of cyclamate or cyclohexylamine on male fertility at the present levels of cyclamate consumption.”