CaptainHolt bloody good point! And what if it was the other way. What if it was a male ward to deal with a specifically male health need (like maternity is specifically male) and there was a blanket ruling that wives could stay overnight with their husbands for support. What do you think the answer to that would be? Different scenario, granted, but what would the reaction be?
Best of it is the current making dads leave at night has been in place for decades. It works. The things that have not worked - shorter stays for women who probably need the extra day or two in hospital, Fewer midwives, A reliance on HCA's and a diminishing number of beds across all wards inc maternity with an increased demand.
All of these are the problems than need to be fixed.