Why bother?

Why is it that I have to write a letter explaining why I am good for a job, making sure to use interesting language and prefect grammar, update a resume' and check it for grammar, shop for the perfect suit, make sure said suit is not wrinkled, be sure to remove any jewelry that would be considered "too much", sit through an long interview during which I have to carefully choose every word I say and behave like the perfect employee, hand write a thank you note, and re-write said thank you note 1-3 times to even have a prayer of maybe getting a job that doesn't involve cleaning up poop or puke most days. It's not necessarily that I mind all this trouble, it's that once i get hired on, they will expect me to do everything just well enough and pretend that I know what I'm doing in the interest of time and quantity instead of letting me take the time to actually do things as thoroughly as I feel I should. Why should I have to give %250 to get the job when what they expect of me once I have it is 80% (or less, depending on the job) at a quick rate? What always happens is, they hire me, I'm too slow and not at all what they need for the job and they either end up firing me or doing work plans and training sessions and such to help me. If you're gonna make me work that hard to get the job in the firt place, then let me work that hard on the job. If you're only gonna expect 80% of me when I get on the job, then let a few typos in my resume' slide damnit.