The only time I hold the mic in my hand is when I'm putting it in the stand. Holding the mic can add noise to a perfectly good take...why risk it?
I found that some people (such as vocalists who can't play an instrument) want to hold it in their hand while vocalists who play guitar, etc., feel awkward holding a mic...it's just what they're used to.
I once recordied a female vocalist who insisted she gave a better performance while holding the mic...she had to move the mic away from her at certain times for such and such reasons..yadda yadda yadda
I set up to record her with 2 mics (the actual recording mic was positioned in front of her at about 11 o'clock - I called it her 'ambiance mic'

and one mic was in her hand). I did a sound check for both mics and when it came time to sing, I just muted the hand mic. She never knew 'her mic' was off. While she was singing she was placing her focus on moving the mic close to & away from her mouth on certain passages (like she does on stage) but throughout all this she remained perfectly still in front of the actual recording mic

Hey, whatever works!