Effectively, this practice is called 'pre-poo'. This is an important part of a hair care routine as it helps you protect your hair from the water you use to wash it. Most people benefit from this practice, however some people, usually depending on the porosity and thickness of their hair, can struggle to use oils on their hair, as the oil weighs their hair down. In this case you can try using a humectant instead as this is lighter, or choose to avoid this practice in your routine.