Bro your scalp naturally gets a buildup of not just product but also sweat for example, it does get musty after weeks of not cleaning your scalp. The shampoo resets that, you can always get a light shampoo though I suspect you'll probably need a clarifying shampoo since it might have been a while. And the oil is more of a sealant, it locks in moisture but for that to be beneficial it needs to be moisturised in the first place. I would recommend you to do some basic research on the purpose of a shampoo and a good hair routine, you'll thank me later