low mounted surrounds ?

[Blown 4.3]

i like looking at all the galleries in here, that is a GREAT feature of this forum.

i have noticed a lot of guys have their surrounds mounted pretty low.
head height or lower (when seated).
i don't get it . if that is the ONLY place that they can be placed, then fine, work with what you have.
imo, these placements are hardly ideal. i mean. how can the sound envelope the room. when the chair, other furniture, and other people, are blocking a direct line from the speakers ? and don't tell me that the sound goes around all that stuff. most of these rooms are using regular bookshelf speakers. so some of the sound gets blocked.

what am i missing ?