When Tim Drake was 2 years old, his parents moved to Metropolis.
They figured it would be safer. Because no parent who genuinely loved their child could ignore the crime statistics that plagued their beloved Gotham, and no parent with any sense in their heads could honestly believe that their baby was safe, as they were out travelling across the world, while their baby slept soundly in his crib miles away in Gotham.
Metropolis was better, the Drakes believed. With baby Tim at home in Metropolis, under Superman's careful guard, no harm would fall to him. They could leave him and come back, and they never needed to feel guilt for their abandonment.
With Superman and a well-paid nanny, Tim was safe.
It was a reasonable train of thought, one made by well-meaning parents with only the very best intentions for their child.
Unfortunately, the Drakes could not begin to imagine that their little boy would develop an independent streak by his ninth birthday. They certainly couldn't imagine that Tim would be so gifted that his every move in Metropolis would be followed by a threat greater than any Tim would have met at the same age, had they stayed in Gotham.
Because neither Superman and the well-paid nanny were any match for the charms of Lex Luthor, upon an impressionable nine year old boy.