Logical/practical objections to marriage:
You don’t have to tell anyone if you don’t want to, but if you actually want to do anything with that next of kin status, revealing to his parents you are in fact married as you sit at his bedside arguing about his life support machine, isn’t going to smooth family relations.
Make a list of all the people in your life who would be upset if they found out you got married and didn’t tell them/invite them.
Marriage does not negate the need for will making and future planning. Many here are treating it like it solves everything. It does not, especially in complicated families with previous marriages and children from previous relationships.
Monogamy and lifelong commitment. Marriage comes with the expectation that it will be to the exclusion of all others and that it is intended for life.
Divorce. To dissolve the partnership you need to prove why you wish to end it. You need to have further contact with someone who may be reluctant to acknowledge you, at best, be violent and abusive towards you, at worst. Divorces can be very complicated, length, and expensive.
To get married more than once you first need to be divorced. If your spouse does not agree to a divorce it can be many years and thousands in court fees before a divorce is granted. That is time spent tied to someone that you do not want to be tied to, and time in which you are not free to enter into the ‘protection’ of marriage with someone else.
Financial implications. Concentrate on the idea that a partnership is financially unequal, and sympathise with the lower earner, and you can see how a marriage, with its implied shared resources, is a good idea, and on an ongoing basis, when the marriage dissolves, offers protection to the less affluent partner. The picture changes if you are bringing much more money or earning potential to the partnership, or if you suddenly find yourself married to a gambling addict or substance abuser, someone in jail, someone tens of thousands in debt. It doesn’t become such a glowing prospect of ongoing support there.
I don’t have an estate liable for IHT.
Hundreds of years of religious and patriarchal traditions in one handy, government sanitised package which may or may not benefit you.