Tonsure or head shave does it help hair growth?

Well there is religious reasons why many people tonsure there head ( in Hindus at times it a sacrifice of symbol of aeasthetics esp. in females). But it is a common belief esp. in some parts of India that if you are losing hair and have thin baby hairs and if you repeatedly shave your head you may grow new hairs or better hairs.
Well shaving or tonsure is only external to skin and does not directly affect the roots which are responsible for the hair growth. The hairs outside the skin does not get the blood supply or nutrition and does not even have any repair capacity and may even be affected by environment.
By removing the outside hairs you are not actually stimulating hair follicle to grow hair. As in case after of shaving of the beard hair the initial stubble feels thorny strong and sharp the initial hair growth after shaving of the head feels thorny sharp and that has perhaps given this belief. But within few days again when the hairs grow little longer that feeling disappears.

Perhaps the benefit of shaving head is the ease of using or applying Minoxidil. Other thing is the illusion of less hair fall because the small hair are not visible when they fall but the long hairs are apparently visible. So person with shaved head or short hair may be psychologically benefited.

In some religion young babies are tonsured with the belief that it will grow new or better hairs. This is not true. In many religions they do not tonsure/shave off their child's hair. At 1 year, the babies usually get mature hair with baby hair falling off. On the other hand, it is know of kids who still have baby hair even after a few tonsures. Shaving does not help hair growth is controlled by genes and hormones.