I believe several factors are at play...
-- Insistence on consistency of style and vision from photographers. When variety has come to be considered bad form within a portfolio, the safest route is to say, "f__k it, take this..."
-- Large scale prints, as are the rage and expection now, often require LF cameras which lend themselves, quite insidiously, to "lining things up." It's a trap I often find myself struggling against.
-- The "dead-pan" aesthetic so popular now favors an uncompromising straight-on type photo.
-- A highly structured shot can use the crutch of that structure to support an otherwise weightless subject.