The Superchargers by us were busy before the Model 3 shipped. They have had a valet at the Dublin, CA SC for quite a while. The supercharging map shows a new set going in a few blocks away this year, but I don't see any activity (permits or building).
I believe part of the issue is that the Dublin SC is right at the East end of the BART line that goes to SF. I guess (and it is only a guess) that some portion of the people valeting in Dublin drop their cars, walk a couple of block and then hop on BART to get into the city. The also have a valet in Mountain View at the Computer Museum which happens to be right by Microsoft, Google, AMD, etc. So I suspect a lot of people drop off their cars, walk to the office and then pickup when charged.