No one in their right mind would, but windscreens as standard have a colour tint (mostly green in this country, but also blue, grey, bronze and what's called "clear solar" which is the purplish/blueish petrol effect you'll often see on Renault's), which will restrict light pass-through more so than a completely clear one, and they also have a layer of laminate between the sheets of glass, which also dampens light passthrough. Hence why there is a tolerance on % of light passthrough
ive noticed this. interesting stuff.