I wonder what it is about our social make-up that makes it acceptable to tell a sound engineer they are doing a bad job?

We don't complain to a performer (mid song) if they are not very good. In fact we tend to feel supportive of them, and afterwards tell them they were very good and they should keep performing.

Most of us generally don't complain in restaurants if the food is bad. How many times have I said "yes everything is fine" to the waiter when really I'm thinking otherwise?! As a nation we are not known for our ability to complain.... except when it comes to sound engineers!

I wonder what it is about the make-up of sound engineers that doesn't like to receive said criticism? Ego dented? Hard work undermined? Stressed?
When was the last time someone told you that you were no good at your job?

The problem of bad sound can arise from two sources:
a) the sound engineer (there are lots of bad sound engineers)
b) circumstances outside the sound engineers control (turn down the brass band at once!)

If you are experiencing bad sound at a concert, its going to be one of the above. They are both very common.

The thing to do before complaining is to try to work out if it is the sound mans fault or not - and then try to make your complaint without disdain! The sound engineer will have been working really hard all day long to get to the point whereby you see him actually mixing the band, and there may well be many underlying factors that are contributing to the bad sound which you may not necessarily be aware of.