Why is the pull out method so "bad"?

I feel like I've been misinformed about the withdrawal or pull out method as a form of birth control. Obviously it's not effective in protecting against STDs which isn't a concern for me but my boyfriend and I have been using withdrawal for a few months as our birth control method and we've been completely fine. Why does everyone give it such a bad rep? if you do it right ( having the guy urinate between each time he ***s ) it seems to be just as effective as a condom. Does anyone agree?