Here in CA lane sharing is a precursor to lane diving and jellied biker on asphalt.

Some bikers will go about 70-80, then dive for that spot in between lanes.

Lane splitting is really not that safe.

The Bots Dots and lane makers do not let your bike track straight.
The paint used for defining lanes has glass in it, that makes it slippery in wet conditions.
There are mirrors on cars-sudden lane changes and people who empty ashtrays, flick ciggies, empty coffee and toss trash onto the road.