If your dispenser is unlimited, your hamster might be tempted to store the food in places where it can go bad quickly
Pet food dispensers usually have a lot more food in them than your hamster will need on a daily basis. If the hamster can collect food from them whenever it chooses, then you might find yourself filling up the food dispenser far more often than you thought you would need to. This is because hamsters love to stash food all around their territory. In the wild, the amount of food would vary a lot, and so they like hiding food in case they run out of it at any point. If you give your hamster a lot of food via the dispenser, then it will probably store a lot of it throughout its cage, food that will be caught up and disposed of when you clean out the cage. This means that a lot of food will be wasted! If you can find a food dispenser that doesn’t allow the hamster access to all the food, then this might be a better option, or you can simply provide their food each day in their food bowl.