Common hair issues like hair fall, dandruff, dry hair, hair greying etc are mainly caused due to damaging scalp microbiome with foaming shampoo.
In some cases other factors like genetics, health issues, hormonal changes, ageing etc are also involved.
A foaming shampoo not only cleans hair but also cleans away good bacteria and scalp oil - the 2 most important things given by nature for healthy hair. It also makes ‘hair’ dry by removing the little moisture which our hair naturally have. This creates a need for conditioner which has conditioning ingredients like silicones which stick to hair making them dull with time.
You need hair oils only if you’re using a foaming shampoo, to counteract the damage caused by it. You don’t need hair oils if you’re not stripping your scalp oil. Scalp oil is the best hair oil for you because it can do things which hair oils cannot do. When you give up foaming shampoo, your scalp will produce excess oil in the first few weeks due to the ‘Transition period’ but it becomes normal with time.