>>82245016
If I had to guess I'd say it's because the nature of the relationship is transformative.
The son goes from a boy to a man, the mom goes from young and energetic to older and more mellow, the mom goes from the caretaker to the one being cared for. But those old memories remain and the couple can always look back fondly on "the old days" so it's the best of both worlds.
Some of us have the running theory Felix and Dexter were flat out groomed by their mothers, if that's the case then you can conclude the same for every other success story.