Why are guys expressionless or smirk when I say hi? Wtf?

So this happens a lot. We could hang out, have a short convo etc. then the next time i'll say hi and they won't say hi back. Then i'll ignore them and they'll smile and say hi like nothing happened. Wtf?
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+1 y
So I guess I won't say hi then...
Why are guys expressionless or smirk when I say hi? Wtf?
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