I am also one of them who sit silently while watching a performance but yes I always clapped after performance by any performer. I think many people do not like to comment or gives their opinion in the public place or it may be possible they do not have enough information to share with others because when we comment on anyone or any performance we have to prove it. Some people have a neutral attitude and they do not care about the performance they just come and watch it , spend some of their time in the show and just go back to their work.
Keep your Face to the SunShine
Some people will be having the habit of searching for faults and they will highlight those faults. If they are not able to find out the faults, they will not appreciate but keep silent as appreciating somebody is not their nature. So you can take the silence of somebody against your performance any way you like. Sometimes we can understand the thoughts of the other person by observing his feelings.
Thoughts exchanged is knowledge gained.
“The most important thing in life is to learn how to give out love, and to let it come in." — Morrie Schwartz
Knowledge is power.