They are most definitely independent contractors. In what way are they not?
They're part-time employees with flexible/voluntary scheduling.
Sure there is. You can choose to not enter based on existing terms. You can try to negotiate and be told no. That's how most open contracts work, including contract to hire firms in US Finance.
That prevents companies from hiring their own employees as contractors and avoiding paying social tax or ensuring annual vacation, etc.
As stated earlier Uber have been banned already in some EU countries altogether unless they choose to register as taxi business and comply with the local (country/municipality) regulations.
[0]: https://www.theinquirer.net/inquirer/news/3020839/uber-loses...