You can say that either
a) Companies examine their specific operation closely and ensure that the manufacturers SOPs accurately reflect the needs of their operation and if not make appropriate adjustments to them, or,
b) Companies do things because they have always done them that way (possibly based on past and irrelevant experience with previous aircraft types, operations, crew experience, etc etc)
Personally, my experience is that (b) is more likely.
I have on a previous type had to do this check on a FFOTD check, not any more though. Plus we use the PA I reckon about 10 times per flight (mixture of left seat, right seat, cabin front and back PA stations) so I think any faults would be quickly identified in normal use and any pre-flight check is superfluous.
Keep it simple and follow the manufacturers advice unless a REAL requirement is identified is my opinion.
HP