Reasons to use a V6 instead of an L6, these controlled the market for quite a while:
1. the supposed "perfect" balance of the L6 isn't that important since external balancers, etc.
2. the length makes a FWD impractical
3. a V6 can be used in all apps
4. the minimum wheelbase of an L6 car is longer than a V8, so it becomes the determining factor for full-size cars that may use either (like the older Lexus)

Wow, 48 volts! Why didn't they think of that years ago?
They did.
Then why isn't it used?
It kills people, and sets things on fire.