Would you want to wear a helmet that had glass protecting the back of your head?Since you had mentioned a helmet, I was thinking more along the line of a gun or a rifle, not a canon.
You have to be careful on how you judge things. Remember that IU there is plot to protect them. However when we do our own debates we can't use Plot as a reason. We have to factor things as close to reality as we can. The fact that ST ships can if they wish hit such small targets means a major risk.And we've seen many shots hit, shall I say, non-specific locations on ships.
And I'm not so sure a window would be so easy to hit.
How many times have we seen this in ST, someone saying "aim for the windows" and people getting blow out because of this?