Brain is very active when you sleep, a lot is happening. Imagine sleep is just a mutex on big set of data on which computation needs to be made, compression, data reorganization, index optimizing. Data that you received that day is segregated , decisions are made which data to keep and which to delete. After that lock is freed and you wake up. If you don't sleep your system will run slower and slower over time and will timeout more and more queries until it will start to return corrupted data. You need to sleep to keep the system healthy.