For stage gear it all comes down to efficiency, size and cost.
In the real rock & Roll world it is often a war over loudness.
Electric guitar and drums have a distinct advantage for getting loud with little input.
Typical lead electric guitar can take 30 watts to 100watts and over power the rest of the stage volume down to 100Hz after which it is no longer audible.
To get to the same level at 40Hz will require a van load of power amps and very large full range and sub woofers.
If you get 60Hz (flat) out of a bass guitar rig it will cost a fortune and will not fit on a night club stage.
A friend had a “HartkeTransporter”http://www.americanmusical.com/Item--i-HAR-410TP-LIST
They claim it is good from 40Hz to 4kHz.
I measured it.
The lowest you could hear it was 80Hz and it never went above 2kHz.
All he cared about was the weight and cost and if he could figure out what key he was in.
In the end you need to be ZZ Top to afford a bass stage rig that goes down to 40Hz.