Shouldn't you be equally surprised that guns have rear sights at all, then? Why is proper sight alignment a good idea during the day but a novelty at night?
How do you propose to find the front sight in the dark, especially against a target wearing dark clothes?
Training for a defensive shot (not target shooting) I don't waste time lining up my sights. I wouldn't need a set of rear sights unless I was shooting someone across the street I guess.
Again... I'm not saying there is no value in them. I just can't see the value from normal applications. If I'm clearing my house at night... I can't see how those 3 glowing dots are going to make a dick of difference. I have a set on my CZ (not my home defense gun)... maybe I should get them out and see what all the buzz is about.
For low-light target shooting, I guess it makes sense if you are shooting at greater than 10yds... for CQC, in the middle of the night... I guess I'm just not seeing it.
Although grabbing it off the night stand... I can definitely see the value in that.