Often things need to be processed or treated to make better and more consistent products. Consumers are also fickle about appearance. You can make powdered sugar by grinding up confectioner's sugar, but the stuff you buy in the store has cornstarch added to prevent clumping. Shredded mozzarella has a powder coating to prevent it from sticking together.

Fresh aloe from the plant doesn't need to worry about mold or spoilage. Something shoved into a bottle, shipped on a truck, and expected to consistently squeezed out of a tube (without drying out or getting gunky) probably needs additives or treatments that change it in order to be safe.