On the note of expecting children - I suspect there's also a broader idea that the current state of affairs isn't permanent. A lot of the petty frustrations of

On the note of expecting children - I suspect there's also a broader idea that the current state of affairs isn't permanent. A lot of the petty frustrations of living together are transient. They change when you change towns, change jobs, have a baby, have that baby grow up into a kid, have your kid move out, and retire. But after all that, there's a long stretch where people's schedules and lives don't necessarily change very much beyond needing more support. That's not universal, people can make all kinds of big changes well past retirement, but it's common enough that people start asking "do I want to deal with this for the rest of my life?" And that doesn't just mean younger people are putting up with bad relationships out of hope for the future. They could potentially be very compatible, making sound decisions like "your sleep schedule clashes with mine, but I'll deal with it for now and it'll be a positive down the line when we have to take care of kids at all hours of the day". It's just that the standard for a 'good' concession to make is different when you're weighing future circumstances against the present than it is when you're going to keep doing the same thing indefinitely.