You're describing theft. Bird didn't abandon their scooter, they know where it is and intended for it to be there.
As noted in another thread here, something being left on the street doesn't mean it's legally abandoned, whether it's a car, a wallet, or an electric scooter.
Most jurisdictions require the (former) owner to intentionally relinquish ownership in order for something to be considered abandoned.
The point is that Bird are leaving their own stuff on the street without asking for permission first. In Sydney that would be considered littering, which is a punishable offence. Similarly if you leave your car for too long in the same car spot, the council will send you an impounding notice and, ultimately, tow the car and send you the invoice.
As noted in another thread here, something being left on the street doesn't mean it's legally abandoned, whether it's a car, a wallet, or an electric scooter.
Most jurisdictions require the (former) owner to intentionally relinquish ownership in order for something to be considered abandoned.