Why dont hairdressers take the highlight right to the hair root?

I've never understood why hairdressers carefully start applying the dye just a millimetre or two away from the root. The stuff must be safe for scalp contact so why dont they take it right to the top?





It means you leave the hairdresser with roots showing already.Why dont hairdressers take the highlight right to the hair root?
lightener can't go directly on the scalp because it can burn the scalp. they put it a little bit away, because the lightener causes heat and the hair shaft to swell usually causing it to gradually descend down the hairshaft closer to the scalp. For regular color application they will put it right on the scalp, that is ok to do, if they don't then its just a personal prefrence.Why dont hairdressers take the highlight right to the hair root?
By allowing the root to be somewhat exposed, it gives it a more natural look to it so it's not so obvious that you dye your hair. Not to mention, those chemicals will probably eat away at your scalp if left on for any length of time. When your hair grows out, the roots won't look so obvious and it can make the hair look naturally highlighted (by the sun), so you don't have to get it dyed as often.
That is a good qusetion, but how much of the sun actually gets to your roots? Highlights are supposed to look like you were out in the sun and it bleached your hair a bit, unless you are getting bizzare colored highlights like green and blue then I don't know.
If you leave the hairdresser with your roots showing, change your hairdresser. If you pay a decent amount they should get it close enough that you do not see roots. Do you see film stars on camera with roots? No!
I've never seen that. I've only seen them start at the root and paint color all the way down
because the foil doesnt go all the way to the root it leaves a small gap between the foil and the hair