It would be ridiculous for Matial Arts Instructors to think they can teach students to defend successfully against all types of fighters in different situations. How would that be possible considering the many variables in these predicaments. The type of outcome will be dependent on the environment (eg street, pub), type of fighter (martial artist, street fighter), calibre of opponent etc.
An Instructor takes great pride when they show their students ways to deal with persons of other styles. Students would then need to learn to deal with fighters of Karate, Jiu Jitsu, Wrestling, Boxing etc just for the sake if they ever come across them in the street (ridiculous). The other problem is your opponent will not wear a label on their clothes, I am Tae Kwon Do so you won't get the 'heads up'. There is also another minus to students in these situations.
Fear of the Consequences: Did you use too much force (you now have to answer for your actions), or not enough force (was is it enough to get you out of trouble)? Good people don't expect or go looking for trouble. Bad people do. You now have disadvantage.
Consequences of the Fear: Pre-fight shakes, loss of motor skills, tunnel vision, sweaty palms, memory loos, timing distortion. These are not going to help your situation.
How to Play it Safe: Your most effective street techniques must be consolidated ready for 'battle'. If you are you are presented with a hostile situation, choosing environment can improve your chances of success. This is why specialized training is required. It is called Reality Based Self Defence! Not all schools are aware of it.
It's not all Bad News: Nevertheless, the more training you do the better off you'll be. Any form of training is going to increase your chance of survival and there are many success stories out there to support it. I believe in just taking things a bit further.