They made an exception for Anakin's age too, (because he's the Kwisatz Haderach or something) but still rammed that "no attachments" crap down his throat, and then act all shocked it blew up in their faces.
If they had simply set Shimi up in a nice little condo on Coruscant, think of all the grief they could have saved themselves. ;)
The prequels unfortunately set up the obvious question, why not take Luke or Leia to Dagobah and train them for the next twenty years?