I had the same view when I was in the Bay Area recently - the hotel sink was square and flat so needed lots of water in it to shave, and the toilets seem to have at least a gallon in before you flush it
Try rinsing your razor in a cup of water. No need to fill up a sink, even at home.
The toilets in SF are so incredibly wasteful. I didn't see any dual flush ones anywhere, and the full flush probably 10x as much water as the toilets in Australia.
American toilets are old-fashioned like that. It's not an SF thing.