Is the warble meant to dissuade the rider from remaining on the sidewalk or is it a prompt for pedestrians to move out of your way by getting startled into jumping into the space you were planning on overtaking them with at the last possible second?

"this might just be something we have to live with, at least for the time being"

No. We don't have to live with morons trundling down the sidewalk on noisemaking scooters. The only people who want this are Stranger interns and cruise ship passengers.

Scooters are super obnoxious.

@4 agreed. They're noisy enough when they're running normally, and then they have this extra noise that's meant to be for safety but it also just goes off indiscriminately. Then there's all the pollution they spew and the thousands of people they kill every yea-oh, hold on a second. You were talking about the SCOOTERS! Okay, nevermind.

They could include a small credit toward a free ride for every x-distance ridden in the proper lane to encourage proper ridership.
Anyway, just buy your own scooter if you care to cut back on waste and pollution. These public ones have a lifespan of a few months.
They are relatively cheap on Ali Express.