This is going to be a noob question but I can't work out what has an effect on shot effiency.

Just to avoid obvious responses.
I know it's calculated shots at goal by shots on target.

Example. 18 shots 10 on target 1 goal=10%

If you have games like I have you've dominated games, had 5x more chances on goal yet draw 1-1 or 2-2.

Is shot conversion down to pure luck or is our orders affecting our players composure?
If you dominate games and deserve a comfortable 3-1 yet finish 1-1 you have a right to feel aggrieved, right? So why is it so common.