Oh, and you wanted examples. I can't say that I know what went into the minds of the people who designed Santa Barbara, but here's how it looks to me:
1. State Street, downtown: Major tourist location. Many bicycle rental shops. There does not need to be a bike lane on State Street, however, since there is one, you aren't going to get tourists riding their rental bikes outside it, or on the sidewalk where bicycling is prohibited.

2. Cabrillo Blvd, downtown: A bike path was installed but since it was closer to the beach than the sidewalk, and much more pleasant for strolling, it was soon converted to a MUP. Cylclists did not want to be obligated to ride on it when Cabrillo is also a major road for cyclists to get where they want to go. So a bike lane also exists on the street, although it's only on one side of the street. You'll observe if you go there that many more people use the bike lane side of the street than use the non-bike lane side of the street. Hard-core riders will use both sides, but you'll see more casual riders on the bike lane side. I personally use the MUP on my way to work and the bike lane on my way home most of the time.

When in the bike lane on Cabrillo, I'm on the street and therefore subject to all the rules of the road, such as traffic signals and crosswalks. I'm integrated into traffic.