Because women wake up to babies at night.
OUCH! Good answer (and totally true).
Totally true that women get up with babies while men roll over and fall back asleep.
However how many years are women doing that for, 15-20?
Waking up for krias shema is 13 till end of life.
I thought women were patur because they needed the time in the morning to put on their sheitels 😉