Saw the same in California. Motorcycles driving between lanes of traffic, passing right-lane traffic on the right.

It was explained that they are allowed to do so legally.

And...if there is an accident, the driver of the vehicle(s) involved are the ones held liable.

At least that was how it was explained by a resident.

I have had motorcycles suddenly appear out of a blind spot...and I do keep alert using all the mirrors.

I assume the motorcyclists who don't have accidents are the ones who are very careful.

An observation from somebody who treated them is that the ones who survive accidents often fall into two classes: Helmet = Broken neck and partial or total paralysis. No helmet = Permanent brain damage and some measure of disability.

Larry