Your parents are lucky to be happy together. I've never been married myself, so I wouldn't know what to say, but, from what I've seen around me - some manage to stay together and be reasonably happy, but then some are clearly unhappy together. Back in the day it was a different culture, that's what people did, they got married, not necessarily out of love. Even if they got bored or cheated on each other, they remained together, because divorce was not a thing.