And I believe there's an entire subgroup of Uber drivers that monitors the current rates and opts to drive only when there's a good enough surge, thereby dynamically creating more supply.
Supply is much less elastic than that. For a short randomized surge of 2 hours, how many new drivers are going to actually come into the road? How many of the rides will complete at that price? How long will the surge last?
No one is dropping what they are doing and commuting an hour for a 2 hour surge. Odds are the surge won’t be present when the drivers arrive.
I only have anecdotes and it’s from Chicago (not SF where indeed a lot of drivers commute an hour to get to a high demand area) but here it’s not that uncommon for people to be able to quickly hop on or off driving on short notice. It probably rarely moves the supply needle more than 10-15% at most but that’s not completely insignificant in comparing vs a less dynamic fleet like taxis.
They would disappear from Uber if they could negotiate a much better price on the curbside.