why we are not using has with he she and it?

we use 'have' with plural and 'has' with singular.. but when we write negative sentence we use 'doesn't' with he, she and it. 'does' is a singular verb and we don't use two singular verb at the same time. so we say 'doesn't have'

We always use "has" as a helping verb with he,she,it,any name or singular subject in present perfect tense. Except for it, we use "has" as a helping verb to show the emotion of present possession.But this rule oniy works for an affirmative sentence. Because when we frame a possessive sentence in interrogative or negative then we use "does" as a helping verb with he,she,it,any name, or singular subject and as we always use the first form of any verb after "does".So, here we use " have" instead of "has". For ex:- She has a beautiful car. Does she have a beautiful car? She doesn't have a beautiful car.

We should use "has" with he, she, it.