I cannot find the insistence in this thread that pens cannot be designed for a gender. There were a few posts that suggested that pens can be genderless, which seems to be the vast majority of the market. To assume the default is masculine is a bit of a stretch, and those that try to appeal very directly to machismo like that Montegrappa Stallone monstrosity get very little appreciation around here. Most depend on relatively simple designs and "safe" color themes to avoid alienating segments of their possible customer base...it is not because the generic pen aesthetic is inherently masculine.
Is it simply a size issue? There are quite a lot of smaller FPs, and there used to be even more when they were actually made to be used in the mass market. They were often advertised in exactly the same sexist language this thread likes to use (let's just confiscate the mancard of any boy who likes a Chalana, shall we?).
There are many aesthetic niches that are poorly represented. I'd say "girly" pens (which I suspect is a gendered stereotype produced and enforced by male-driven systems) enjoy a better chunk of the market than do ones that pander to a flamboyantly "masculine" crowd.