It is because many people want to be perfect just at the start, but there is always room to improvement, but people don't accept that, so they don't want to be better than what they are already, so the don't revise themselves or anything.
Some people find it hard to revise at home because you can get loads of distractions, whereas at school or a library it is a place where you have to work so you will be more focused and will be able to learn more by yourself
