Lack of sexual morphology in clinically significant fungi.

I'm in a medical mycology class and one of the first things we learn is that all clinically significant fungi are identified by their asexual morphology. I was wondering about this and I think it's because there's no need for sex when you have a host to live in. Sex is used in nature to cope with harsh conditions and life between someone's toes or in their hair, nails, bloodstream or under their skin is just rosy. What do you all think? Am I right or am I right??