It can happen. It just doesn't happen often. You could have been one of those who fall in the low percentage who does get an std orally. Plus, often, oral sex leads to intercourse. When you are caught up in the moment, you don't really want to stop to put on a condom, then go back to what you were doing. A lot of times, that is what happens. People say to heck with it... You know?
thank you so much, then why do they insist that we have PROTECTED oral sex if the chances were low?
Your chances are very low. Getting an std orally is very rare. The bacteria do not like the conditions in the mouth.