Why do girls in thia have to say ka after speaking?

Ka is know as a female particle in the Thai language. Females say Ka after most sentences as a way of being polite. Similarly male speakers will say krup at the end of most sentence's. There are also other spoken difference in the Thai language depending on whether the speaker is male or female. For example the pronoun I/me/my for Thai females is dee-chun while for Thai males it is pom.