My bet is on the technology, history, and tradition.
Basically, bass frequencies are hard to create without modern tech.
Here's my take on this.
Most old (pre-Baroque) music is centered around octaves that were higher than the centuries that followed. Cellos, bassoons, bass lutes were pretty much the only portable instruments that could produce the required bass lines. At that time there were two families of popular bowed string instruments, the violin family (modern violins, violas, and cellos) and viol family (modern double bass). The former are almost always fretless, are tuned in fifths, and have bodies where the curve of the wood joins the neck horizontally. Viols are often fretted, tuned in fourths, and generally have bodies where the curve of the body tapers up to neck (look at pictures of violin bodys and bass bodies and you'll easily see this).
Viols were replaced mostly by violins somewhere between 1700-1800 as the violin family is louder and technically more adept with the exception of the bass viol (now double bass) as low freq technique does not work so well tuned in fifths.
For about 150 years your choices for a portable bass were limited to a double bass or a tuba. Woodwinds generally don't work as well and were not as popular. It's still not uncommon in some realms for doubling on bass to mean being able to play bass and tuba. I'd have to check my references as to when E A D G became standard but I think it was more or less settled by the 1800's. The electric bass derives its tuning from that as early on all electric bass players had been double bass players. That changed, probably around the end of the 50s I'd imagine when guitar players and novices took it up. These folks were not limited by pre-conceptions of acoustic music and so let their imagination take the instruments to all sorts of new places including higher and lower tunings. This became more feasible over time as the amplification, reproduction, and availability of improved hardware like strings and pickups that could reproduce these lower frequencies in a pleasing manner. Try listening to a low B on a 50s phonograph or playing through it a pre-50's amplifier. Not recommended.
It's like bluegrass or jazz really, a lot of bluegrass is in the Key of G because of the instrument tunings, and early jazz in Bb because of brass tuning. I think popular music might have been a little different if the electric bass had a B string early on and assuming that the reproduction technology was available, but I think the primary driver of the keys of popular music is the guitar tuning not the bass. And E on a guitar is definitely more accessible than other keys. If one looks at the effect of the low B on current popular music, my opinion is that it has reduced this E lock and helped free the music to move to other keys.