Because you aren't disadvantaged in any way because of your atheism, short of having to endure some awful faux-intellectual conversations. Minority doesn't equal disadvantaged. I'm not sure what part of Texas you are from, but I don't think I've ever seen any persecution of atheists.
Are you kidding me? You know how volatile this topic is in Texas? I mean look at this forum, I asked a simple question and the first couple of post assumed I was a hedonistic demon spawn. There are PLENTY of cases of people being fired which lead back to their atheism coming to the forefront.
It's been my experience that any "persecution" an atheist experiences is due to how intolerable they are about being an atheist (not implying that you are this way). Same thing for Christians or anyone else who feels strongly about anything, really. It's not persecution if people dislike you for being an asshole.
That's true on some cases, probably less so where I'm from. I don't know where you are writing from but I get a lot of the "You don't have morals" kind of talk any time I let people know that I'm not part of their club and it's a pretty compelling reason for employers (or any social function) not to allow you access.
Write about your economic hardships. That's more compelling, anyway.
I most likely will, if admissions boards are even a fraction of as bigoted as this forum has been it's probably a good idea to hide (and lie, I guess?) about my own personal beliefs. Lol, how's that for morality?