Engineers understand that their appearance only bothers other people and therefore it is not worth optimizing. It's a small wonder, since the engineers on the starship are portrayed as heroes, occasionally even having sex with aliens. This is much more glamorous than the real life of an engineer, which consists of hiding from the universe and having sex without the participation of other life forms. Dating is never easy for engineers. A normal person will employ various indirect and duplicitous methods to create a false impression of attractiveness.
Engineers are incapable of placing appearance above function.
For society, it's probably a good thing that engineers value function over appearance. For example, you wouldn't want engineers to build nuclear power plants that only like they would keep all the radiation inside. You have to consider the global perspective. But the engineer's emphasis on function over form is a big disadvantage for dating, where the goal is to act phony until the other person loves you for the person that you are. Engineers don't like to make small talk because no useful information is exchanged.