In some cases, you see that because the owner either refuses to compromise the vest look for the best sound, or they simply don’t believe the difference is worth compromising the look (WAF can come into play). Of course, they might have found that what you are questioning, is the best placement for sound. Can’t speculate which case it is, with certainty.
Question about speaker angle
I've always been under the impression that your front main speakers should be angled so that the "face" of the speaker is basically perpendicular with the listener's face when viewing the speakers from the sweet spot. I do however see others placing the speakers parallel or inline with the surface of the wall behind the speakers. I'm wondering, how much loss to the sonic sound stage this creates.