The Medrash (Bereishis Rabbah 17:8) asks this question, and R’ Yehoshua answers: Adam HaRishon was created from earth, and earth doesn’t rot, therefore no perfume is needed. Chavah, however, was created from bone which rots, therefore, she needs perfume to cover up the smell. The Medrash brings a moshal: If one leaves unsalted meat out for three days it immediately begins to smell, if, however, one leaves earth out it doesn’t.
The Eitz Yosef explains that although Chavah was created from bone and bone doesn’t rot, there was also meat inside this bone and this meat rots.