OP - imagine the worst happens and your DP was hit by a car tomorrow. Do you own your home? Even if you are on the deeds and own half, who would get the other half? Could you afford to buy them out? Can you imagine greiving for him and packing up the house to move? If you rent, is your name on the tenancy? (I only rented with DH before married in flats I could afford by myself so I've no idea where you stand if your partner dies and you can't afford the rent on your own, I assume you get given notice and have to leave.)
Sod all of that, if he died tomorrow, even if you got the house, where do you stand on access to money in bank accounts in his name, including joint accounts? If that got frozen until it was sorted out, that could be a couple of months, where would you stand on paying the gas bill now? Would you be even allowed to talkto the utilities companies on behalf of his 'estate'? (I don't know this, you'll need to take legal advice, but this is the sort of question a 'partner' rather than 'wife' needs to ask)
If you're not the next of kin, his body wouldn't be released to you. You don't get to organise the funeral and don't automatically get an invite.
Now flip it all around, and imagine it's him dealing with losing you and having no right over anything. Just seems cruel to leave him in that shitty situation without trying to do everything you can to make it easier - even if you don't get married, you should get all those bits of paper in place. Only kind thing to do if you do love the man.