He or She?

Why do we have to use both? I know in our modern world and with women’s rights we cannot only say ‘he’ all the time. But why both? Why not ‘she’ sometimes and ‘he’ sometimes? Why use both each and every time? Actually, each and every bothers me too, but that is a different story.
The Bible refers to the human race as ‘man.’ I never had a problem knowing what ‘man’ meant. Since a child, I knew and understood ‘man’ meant mankind. Or, is that mankind or womankind?
Actually, it is fine and proper to use he for the pronoun all the time. I am not highly educated, but I do not think of he as only males when I read a book or article. Does higher education make people that picky? Maybe there is something to just good old horse sense. With all the new dictionaries containing so many new words why can’t someone devise one word to represent ‘he or she’? But then, I guess he or she has not thought of it!