I don't know about the US, but in Germany coops have pretty strict auditing guidelines. Since Hollywood accounting would divert money to the coop, which is also owned by the drivers, you would by diverting money from the drivers to the drivers, which obviously doesn't make any sense.

Of course there are also concerns that the coop administration might be too fat and lining their own pockets, but through the auditing combined with the fact that the board is normally elected by the members, the members have quite some control measures to keep the administration honest.

They're also owned by the drivers, so one would hope that would help with transparency