I really don’t understand the hostility to wanting the same rights for cohabiting couples as married ones I have to say. Why do people seem so angry about it? If you got married and you like it why are mad that others who haven’t done it could be legally protected in case Of death etc?
I don't think there's hostility, but, as has been said, it's just a case of actively choosing to have both the rights and responsibilities of marriage or otherwise (by default) not choosing to have either.
Stirling Moss was racing cars at the highest level for years, but didn't have a driving licence for a number of years, meaning that he couldn't legally pootle around town to go to Asda. Later on, I believe, he did pass his test (which I'm sure didn't cause him any difficulties at all), because he wanted those rights - along with the responsibility to tax, MoT and insure his car, if he then chose to own one. In his case, nobody doubts his abilities, but there's still a legal avenue you can choose or not choose to take, to gain the legal rights and recognition.
I don't know if it's still the case, but there was a system a few years back whereby people coming to live in the UK had to pass a test to prove that they had a reasonable level of comprehension of the English language. Included in this were people from countries like the USA and Australia, but they still had to take the (for them very easy) test if they wanted the associated benefits.
As PP have said, legally forcing people to take on the mantle of effectively being married - the rights and responsibilities - would be outrageous. Isn't forced marriage actually illegal, anyway?
How is anybody else to know whether the (non-blood related) adult you live with (for however long), is your romantic partner with whom you want to share your whole life, a casual partner (Mr Right-Now), a mutual friend with benefits but nothing more, a very close lifelong friend but one with whom you share no romantic attraction, a lodger or even a housemate whom you hate, but have no other feasible option but to share a dwelling with? What if you share a house with more than one non-related adult? How does the state decide which one to assign as your de facto husband or wife?
You could say the same about birth certificates - why does the government force you to register a birth? You know you're the parents, so why does anything else matter. The government could just randomly assign a name to your baby and write to the mother (if the delivery hospital has passed on the details of the birth's having taken place) to tell her what name her baby is to be officially known as.
There's no such thing as being a bit married - you either are or you aren't. Would you prefer individuals to be allowed to freely opt in and apply for that status for themselves (or otherwise choose not to) or would you rather some government department monitor your life and then arbitrarily decide whether or not they consider you to be married to another apparently associated adult at some stage when they see fit?