I think it's fear. It's easier to "be normal" because it doesn't feel as risky. But then, not every employer responds well to that sort of thing either. I've tried this same approach more than once, and it's never worked yet. Not a valid statistical sample, but people seem to be afraid to hire someone who is forthright.
Although, I don't think it's a question of whether I'm forthright or not, that's too simple. The whole interview process, starting with the initial letter/application is actually a kind of mating ritual. If you get the sequence right back and forth, then you get a chance to get hired. If you don't get the sequence right then you make people feel uncomfortable, and they won't hire you probably.
Basically, by being brash during this process, you make people wonder if you're capable of the mating ritual, and if you aren't, then why not? Are you socially inept? Professionally incompetent?
The off chance that you're perfectly ept and competent, but have just chosen to apply for a job in an unconventional way is too great a risk for most people, so they pass, and look for the next guy who follows the rules of the ritual.