It isn't. It's a real mess, and it affects carers and widows hugely, I don't think anyone ever thought it through, or even cared. I was widowed at the age of 54. There is no Widows Pension any more for someone in my situation, only Bereavement Allowance which lasts for just one year. Three months after my OH died, I was seriously disabled in a car crash, couldn't walk at all without terrible pain. Normal work out of the question. My husband restored vintage lorries, and had significant stock (30 tons!). I gradually sold them to earn money, but it was incredibly difficult, my eldest son had to help me. My husband wanted to pay into a private pension for me when I was young. Government regulations prohibited this as I wasn't working, just saving the state thousands of pounds each year caring for our son with severe learning difficulties. When I finished my degree about 20 years ago, I was offered a really good job, but with no other care available in the area, I had to turn it down.
I'm left feeling that the needs of women still don't matter.