Why can attributive clauses use that when expressing people?

Reason: that is often used as a relative pronoun, which can refer to people or things. What can be used instead of that when referring to things, and what can be used instead when referring to people? This is usually used in the following situations.

1, that means someone, usually someone. For example:

He is a man who never loses. He is a man who is never at a loss.

2. The main sentence is a special interrogative sentence with the subject of who, so as to avoid repetition. For example:

Who is the man who is talking with our headmaster? Who is the man talking to our headmaster?

There is the same tense before the antecedent. For example:

This is the man who gave us a report last year. This is the man who gave us a report last year.

Extended data:

In addition to expressing people, there are other occasions for use:

1, when the word modified by the attributive clause is any, nothing, everything or the noun is also modified by nothing, little, some, all, no, much, the very, the only.

He wrote down everything the teacher said. He wrote down everything the teacher said.

Tom told me some jokes he heard from his friends. ? Tom told me some jokes he heard from his friends.

2. When the word modified by the attributive clause is also modified by ordinal number, the superlative adjective. This is the first gift my grandmother received. This is the first gift my grandmother received.

3. When the noun modified by the attributive clause is a combination of human and non-human (serious face). Example:

Do you remember the boy and his dog that we met last weekend? Remember the little boy and his dog that we saw last weekend?