Why can it take up to 60 days to receive the first payment?

Why can it take up to 60 days to receive the first payment?

As a publisher, we have to wait for advertisers to pay us before we can pay you.  

1st - We report stats to advertisers.
2nd - We bill for those advertisements 30 days later.
3rd - Advertisers pay us sometimes 30 days later.
4th - Drivers are paid a revenue share for ads as soon as we get paid.