Should I have to add files to git every time I want to commit?

This allows you to separate commits by edits. If you only want to commit these files now, under one commit, and then these next files now, under a second commit, you could do:

git add files_under_one_topic
git commit -m "this is about one thing"

git add files_left_over_to_commit_about_a_completely_different_topic
git commit -m "this is about another thing."