My employer is of course just one and not representative of every company. But my work/indurance is happy to accept long term domestic partner in lieu of marriage. As long as you swear to be in a long term committed relationship and live together, it's fine.

That opens up an entirely different discussion, which is why should health insurance be tied to a job? This is also uniquely American. Is your home insurance tied to your job? Is your car insurance tied to your job? Is your life insurance? Doesn’t make sense that your health insurance should be. What happens if you get laid off or you decide you don’t want to work for this company any more or you want to take another opportunity? Now your health insurance or your health insurance costs might both change. And you might have to go through the same hoops again to get a domestic partner installed, etc.

FWIW, it has become increasingly common in the US (or at least the parts I’ve lived in) to allow adding an informal domestic partner to your health insurance, no marriage required. IIRC, there is a tax quirk if you do it but I haven’t done it in many years.