Why is it that women don’t perform haseivah (leaning at Seder Night)?
It says in Shulchan Aruch only nashim chashuvos (important women) should lean, and in fact our women get that din and really should lean. Even still we rely on the opinion of the Raavyah for women and don’t make haseivah…
But why not…We see that women have the same exact din as men when it comes to the Seder for all the laws and everything done by the Seder. However, when it comes to a haseivah, that there would be a question postfactum what to do if a person didn’t make haseivah, why is it so clear-cut that the women don’t perform haseivah?
Many discuss this difficult question.
One approach is that in principle, the halachah certainly follows the Raavyah, whereby there is no obligation of leaning today. It is not the way of cheirus (freedom) to lean as we eat, and therefore the formal obligation of Chazal does not apply (see also Maharil 18b who writes that leaning makes us look like we’re ill; see Hagahos Maimoni, Chametz U-Matzah 3b writes that sitting upright is the manner of cheirus!).
However, men continued to lean as they ate, wishing to give an expression to the special nature of eating at the Seder, even though there is no obligation. Women did not take on this practice.
Therefore, it remains obligatory, by dint of the custom, for men to lean, but this obligation does not apply to women.
Other explanations have also been offered for this question; perhaps the questioner can add some in comments.