You don't have to but if you don't it gets untidy.
The commonality between your hair and nails, and yard grass, is they all continually grow.
They have no nerve endings.
Hair and fingernails always grow continuously unless intentionally trimmed or cut. Additionally, plants and trees grow as long as they have access to sunlight, water, and nutrients.
Your hair contains no nerve cells (the things that feel). Much like your fingernails. It's prettymuch just dead.
Hair, fingernails and toenails, and old dead calloused skin.
Rhinoceros horns are made out of solid keratin. Keratin is the same material that fingernails and hair are made of. Also like fingernails, the horn can grow back if it is cut.
My neighbor is always crabby when you cut across her lawn.
I think you mean do not "HURT" when cut, and that would be toenails, fingernails, and hair. These parts are all "dead", so to speak, and have no nerve endings.
Hair does not have blood vessels or nerves running through it. Also hair is made from basically the same thing as fingernails or toenails and it doesn't hurt to cut nails!
Can u cut your fingernails to pass a drug test
because it will overgrow if you don't
There is no exact start time. It is an ongoing process. Think of it as cutting the lawn or getting a hair cut. The grass and the hair do not stop and start, it continues until you have to cut it again.