Some of us are just too nice and can't criticize
...seriously there is a fine line one needs to toe when making comments on performances. Too tough, and feelings could be hurt, and friendships could be lost. But all nice, all the time, comments can come across phony. Nothing worse than "Nice Job", "Keep Up The Good Work". Reminds me of the old Bandstand days when Dick Clark had kids evaluate a new record. They almost all had the same line... "Well, it had a good beat, and it was easy to dance to"
Generic responses are not helpful, better to say nothing.
So my (new) policy... If it just plain bad, I won't say anything, unless the artist WANTS me to point out any flaws I hear or see. However if it's a good performance I almost always let him know that's it's either great, or try to point out what could make a 'good' into a 'great'. (not that I'm an expert, just try to help)
Again, it's not easy being a 'judge', not all of us can be a Simon Cowell, and be brutaly honest