It reduces the risk for the farmer because they only have to pay based on what they are able to grow instead of a fixed amount as seen in most cash-rent arrangements. The landowner stands to lose if the crop is a failure, but can make more if the crop is a success.
The term may also come with some historical meaning, but that is what sharecropping has come to mean today.
Edit: Down vote me if you wish, but that is what sharecropping is in the rural community. Speaking as a farmer, sharecropping is a great way to access land in a low-risk way. I don't know why sharecropping land is seen as a negative.