Never thought about this before but yes, I think you are right. However, they serve different purposes. MINUM and MAKAN don't really need an object. They are both intransitive and transitive while MEMINUM and MEMAKAN do need an object following them (transitive).
You can say: SAYA MAKAN or SAYA MAKAN NASI, both are grammatically correct. But you can only say: SAYA MEMAKAN NASI and when you only say SAYA MEMAKAN, something is missing - the object.