I've worked in tech companies where the only people not wearing jeans were secretaries, sales reps, and people who have job interviews that day. Dressing up the wrong way can be a problem in that environment, even if the clothes are comfortable.

(I'm no longer working in labs. Now I'm freelancing, where actively performing femininity helps. I mean, it helps me get clients, not just letting me go downtown without pants when it's 90F.)