This may come as a surprise to you but married couples are bound by their vows of marriage to live chastely as well.
It should come as NO surprise to any Catholic. If they are given proper catechesis on the VOCATION of marriage, this is very apparent. But alas, (sigh), all too often marriage isn't seen as a VOCATION.
I'm not sure I understand you. Not to overdo sex within a marriage, perhaps, but certainly not to avoid it. Maybe it's just a semantic thing on the meaning of chaste. I've always taken it to connote abstention.