Because people try commit fraud and do shady stuff. We make it very easy for someone to collect money on one service, and get paid on another. A setup like that is ideal for fraudsters to exploit. Without some sort of opaque system around processing payments we would make it easy for bad actors to attempt to reverse engineer the system.
If you are concerned about payout processing times then we recommend using the “Direct payments” mode, which will enable you to get paid immediately at the time of the transaction.