Because it’s pronounced differently. “Rachael” is pronounced as Rah-kell’, and Rachel is pronounced as Ray’chel. read more
Being a Rachael is not an easy life. When people write your name they will put "Rachel" or my personal favorite "Racheal". People don't really ask how to spell it so I always say "Rachael with an ael" and sometimes that works and sometimes they still write "Rachel". read more