I think, the root cause is that we human beings forget easily, and do not absorb info fast enough. It's not that we are not learning the first time.

The benefits of repetition, is to make that memory stronger, and the extra time spent, will also enable you to learn other aspects which you didn't notice the first time you learn it (effected by processing speed). For example, you didn't realise your master flatten the chicken first instead of chopping it immediately.

Sometimes it is a matter of preferences, if you prefer something, you tend to think and delve on it longer. This makes stronger memory bonds. Also perchance, when we sleep, our brains will reprocess some info we see in the day, if the brain determines the lesson as important, it might reinforce it into memory.