Good question and your points are valid regarding the two industries. However, pulling the wheel and inspecting brake shoes (especially rotors) is much less labor intensive when compared to pulling a transmission (especially in a 3/4 ton truck, 4x4, etc). I would not think one would simply pull a transmission out and disassemble for a routine inspection (unless a racecar), hence changing a $40.00 component "while you're in there."
