You don't know other people's innermost feelings; only their external 'front'.
Everybody thinks I am a sociable, confident, outgoing person. People always express shock when I say I am shy, or feel intimated, because their perception of me is so different to how i actually feel. It just shows how good my masking techniques are i suppose!
These days I can speak to anybody, be friendly, act confident, deal with difficult situations with grace, but it's a learned behaviour and one I have had to work hard to cultivate. When I was a teenager I could barely speak to anybody, my throat just closed up if I tried, my hands shook so badly i couldnt write or hold a drink, I'd just hide in the shadows wishing I could be different, better, more confident. That's no way to live, so I learned to fake it; my life and interpersonal relationships improved immeasurably as a consequence.
If you want to be more confident you can learn how, but don't criticise and judge others for 'lying' or 'being fake' based on your own skewed perceptions of their personalities.