Your statement is true in San Francisco, but Pacific time zone also encompasses Oakland, south bay, los Angeles, and san Diego, where relatively few people commute using Uber compared to going out using Uber.
From personal experience, having driven for Lyft and Uber I'm two cities (Sf, sd) surge in SF does get acutely high in the morning, more broadly in the evening (work departure times are spread out over a wide range of hours), and acute around 2am. In California, bar closures statewide are 2am at the latest, so that accounts for unified departure times in multiple markets.
From personal experience, having driven for Lyft and Uber I'm two cities (Sf, sd) surge in SF does get acutely high in the morning, more broadly in the evening (work departure times are spread out over a wide range of hours), and acute around 2am. In California, bar closures statewide are 2am at the latest, so that accounts for unified departure times in multiple markets.