As always, I can't make any truly educated guesses, but I'd say a factor is (as I think has been mentioned) that nowadays, it is normal for women to have stereotypically 'masculine' hobbies and interests - a woman could be a boat enthusiast or a player of video games or even something like a bodybuilder, traditionally very masculine. However, a man can't really indulge in stereotypically feminine activities - shopping, using makeup, et cetera - because that's seen as weird.
As such, if a woman were to try and become a man, the issues are less around changing behaviours and more about the biological aspects, such as hormone therapy and reductive surgery. Overcompensating and acting incredibly manly might be an issue, but frankly I haven't heard much about it.
However, if a man wants to become a woman, he needs to 'act like a woman' as well as the physical changes, and even assuming they're genuinely transgender it's likely they've never, say, applied makeup before in their lives. This is why (besides crippling autism) a lot of the MtF lolcows often have ghastly hair (like Chris) or clown-like makeup (numerous examples) - they think 'women have long hair/makeup' and never properly look into how it works. Likewise with the crippling cutesiness you tend to see - they're 'acting girly' because that's the stereotype. This, of course, is less evident with sane MtF people, as they actually put effort into appearing female (even if they're just not cut out for it).
TL;DR: Assuming we're talking about transtrenders, it's because they have no idea what women do besides the stereotypes they're apparently so adamant about destroying.