counterpoint: buses have greater reach and are potentially cheaper to add and operate than BART trains on the margin. If the primary transbay tube goes down in a quake we'll benefit from the diversification.
I know you're counterpointing here, but really it nets out the same. Connecting transport increases it's potential.
It baffles me that SF chooses not to integrate Bus, BART and Caltrain.
SF does not choose that. In fact SF has long chosen to integrate bus, Muni rail, and BART, and more recently also Caltrain, though getting the Caltrain part done has been hampered by a number of problems, including the cost overruns of Transbay Transit Center’s first phase, which have eaten up the money for the second phase.
Edit: by "don't coordinate," I mean there are no timed transfers between systems.