Inheritances usually don't come early. Grandma Holwick showed my Mom some cherished heirlooms. Someday, these will all be yours. My Mom slobbered over them, imagining where she would put each one. Grandma managed to live another 40 years.
Mom insists it was out of spite.
In Israel, early inheritance was legal but not polite. In effect, it's like asking dad to drop dead. Here, Luke seems to describe it as part of love of God. If we want to go, he lets us. The son goes, as soon as possible and as far as possible.