MY COMMENTS ON THIS ARTICLE:ANYWAY from the article my only question is what about men who release sperm at night. They are impure for a day and therefore have to be seperated as well.
And what about women after they give birth I assume they can be with the child even though they are impure and the child has this impurity as well which can easily be removed after the period ends by washing their clothes as well. In fact it may give them this special bonding with the child although obviously a boy has to be circumcised at 8 days. Here is the article
Read more: Kinship, marriage, and family - Karaites http://www.everyculture.com/Africa-Middle-East/Karaites-Kinship-Marriage-and-Family.html#ixzz1exiBVpLm
As to why the impurity it is likely from what I read to remind women of not wasting their child bearing years and for men not to think physical attraction to women is just for pleasure without any responsibility. Does anyone actually do this in Israel? Does anyone know.
Also while Karaites do want their women dress in an appropriate manner I would think from reading this unlike the Rabbis they let people use their sense in this and not micromanage it themselves.
And for helping men not waste their sperm I would think think they wouldn't want women to just play games with men in flirting with them to arouse them when they aren't interested in arousing men so they will have relations and bring new life into the world.