World Building | Immortality, the Downward Spiral, and the Endless Hijinx of Finding Love
In the event of find one's self with the inability to die in the multiverse, the future in their life would be an arduous and agonizing mix of emotions that even the most unstable would be unable to comprehend. Few would understand their actions, nor would they ever even if they tried. Loneliness is as an occupational hazard for most, and a broken heart is, at worst, abject cruelty.
As much as it is tempting for those to do what ever they want, where ever they want, consequences still apply. Being Immortal doesn't stop the pain of trying to live, nor does it excuse you from actions which harm those with a limited life.
Additionally, if worst comes to worst, if they are in a situation where the people who caught them know about their immortality and have a heavy grudge... Humanitarianism need not apply...
In the life of those who wish to not travel alone, love is dangerous to their mental psyche. There will be days where settling down would have been a good choice, and it could still be decent even now. But remember, they can either tell them upfront, or just hide it.
Most choose the latter option, as the typical methods of hiding their true nature would be an accident leading to a disappearance or just falsified self-termination. Rarely do they full explain themselves ahead of all this, mostly due to the strain it puts on the relationship between the lovers, the children, and their families.