I guess it doesn't appear in the usual stories. I was also surprised he got married and had a kid about the time he wandered off to be spiritual, it seems which doesn't often seem to be mentioned.
The separation was a during his spiritual search. After he attained what he was looking for he reunited with his son.
Sometimes we have to go away to figure things out. After he reached his goal, the Buddha spent the next fifty years surrounded by people whom he taught and counseled.
Let me flip it for you. What about Alexander the great, or other historical figures? Shouldn't he have stayed home with his family instead of starting a senseless war and then dying in India?
How come this double standard is always trotted out against the Buddha, when all these other conquering, massacring guys get away with it?
"Kill the Buddah if you encounter him" might be something to do with it but might be unrelated?
I also remember something about how Buddah can be found in the butchers shop, as if to say "stop looking for him as if he was something outside you, you are doing it wrong." Or about how if you get buddhahood you can be quite comfortable cutting up dead animals (i.e. Buddah is comfortable in nature)
I heard there are lot of stories out there of so called Zen Masters who claim to have achieved enlightenment (those according to your example, who can drink alcohol, kill animals for eating them) who get drunk and otherwise act weirdly and it is excused with "well, we cannot understand them, they are enlightened and we not, so we cannot see the wisdom in their actions".
I have not much personal experience with Zen, but heard that this is not so uncommon.
But of course, this doesn't say, that there are personal benefits in meditating, leaving a life without drugs, have a focused mind etc. - but maybe this things are mainly a new, western construct, attached to the base religion of Buddhism.