May I ask why do you want to look like a man other than for lulz? Nothing is preventing you from engaging in "manly" activities as a woman.
The most honest reason I can find is that, well, it appeals to/really interests me. I like mens' fashion and styles as well as female ones, and I'm curious about dressing, well, masculine. I guess it may be a little silly, but it's not because I find it 'funny'. Who knows, when I try it out I may find it less fun than I thought. Or, maybe I'll like it a lot more. I figure if you ask someone why they crossdress you'll get a different answer each time ^^
And I definitely do "guy" things and still consider myself female. I don't think the activities you do decide your gender, but rather what you feel or brain/psychology stuff. I hope I'm not being too confusing.
Maybe it's like I'm an omnivore, but I sometimes like eating vegan stuff because I like that too...?