The critical value created when shooting a great portrait is tied to building impact that lasts. Psychologically, humans have evolved to take notice of sexually attractive people, focus on them briefly, then completely forget. This phenomena helps maximize genetic quality in a population but can also have an impact on how viewers remember your sexy photos.
There is nothing wrong with shooting sexy subjects, rather, shooting attractive images can be tremendously rewarding to the client. However, it is your job to add more depth to the image than just being “sexy.” Sexy needs to be limited to being an aspect of the image rather than the primary focus of it.