rabeinu yona has 3 reasons for the mitzvah of eating on erev yom kippur. 1)Since you cant do vesomachtoh v’chagecho on yom kippur we do it on ever yom kippur. 2)To give us koach to fast for yom kippur (and its only a hechsher mitvah) 3) to show that were happy that we are getting a kapora
the ksav sofer says l’fi r’yonas reasons, women are chiyuv.
(lichoirah R’ akiva eiger is going lefi reason 2)