Oh, I'm quite aware that it could end (whether due to death or divorce). I choose not to spend my time dwelling on the possibility, because that would be like living in hopelessness. There are a lot of bad things that might happen to us in the future, and some are even likely, but living in constant dread for the future is joylessness.
If I was to marry - I'd have to marry someone with the same level of income, spending/saving habits, and so forth for the marriage to be "equal" in the eyes of the law. As it stands - I don't consider that as much of a factor for my relationships because I'm an extremely giving person. However, my willingness to give everything to someone ends when the relationship does. If I choose to not interact with this person anymore then why should I be in their debt until the end of time?
It's not worth it. It creates a perverse power incentive for people in the marriage as well. Again - maybe you're not in that situation but I was making $400K+ and they were making $0 for years. They had no intention of ever working because they knew I could pay for everything. It went from gratefulness in our first year to entitlement by the end of our relationship and had spread like a plague ruining everything. I cannot fathom how much they would feel entitled to if we had been legally married - even if they contributed literally nothing. And I'm dead serious - they didn't do housework or child raising or anything either - they did nothing and yet there are no absolutely no enforceable protections for people like myself... BESIDES not marrying - which is what I advocate for.
I advocate for love, support, giving, and so much but it needs to be on your terms. It cannot be on the terms of some archaic governmental, cultural, and religious institution.
If we can fix the system, then no 'hopelessness' may anymore be involved. That's what we need to push for. As of now, the system for broken marriages is hopelessly bad.
My advice to all would be that even when in a good marriage, to the extent you can, don't make choices that would make the end of it hopeless for you.