Do you encounter your manager asking you "why" as his first question, the second question and perhaps his last question too?

Rarely. 

Unless there is lack of clarity or if any doubt arise. 

rarely

When was it strange

In all cases, the best performing understandable commands

thanks for the invitation

There is a terminology calls7 whys questioner which leading you to the nearest accurate answer? so "WHY" it's for justification nothing personal?

Have an nice day.