Sometimes it means "We don't want to spend a lot of money training this guy who we won't be able to retain if he gets a better offer."
At really entry-level jobs like fast food, where training is quick and turnover is always high, it sometimes also means "This guy might be able to read the workers' rights poster on the door and explain the workers' comp program to the idiot who spilled boiling grease on his foot.
Historically, it's been alleged that some 'celibate' Catholic bishops fucked women. When the resulting bastard children grew up, they were rewarded with coveted Church appointments. If anyone noticed the apparent favoritism, they blamed the adultery on their brother, saying the appointee was a nephew (it: nipote) rather than the priest's own illegitimate son. Thus the origin of the term nepotism.
Probably some of them had different tastes and realized that fucking boys leaves less evidence.