A scary story told to naughty children
Children are rare to find within Synthacrosia, and hard to deal with. The Tower exists within Purgatory, and only those who have died arrive at the tower. Once a soul is within the afterlife, they stay forever at the age they were when the died -- in the tower, souls no longer age. This means any child in Synthacrosia would've had to have died in their childhood. It also means they'll stay as a child for eternity. There was a plan for this, of course. In the early days of Synthacrosia's operation, before Locorin disappeared, a group worked to select and train souls into childcare roles. They would essentially adopt these eternal children, and care for them until the end of time. The childcare givers would try to teach the children, and to help them grow; but as aging was a process that never occurred, maturity was never reached. The children's brains were constantly stuck in a state of regrowth.
Oh, you don't want to sleep, eh? You know who else didn't want sleep? Old man Jacobsen. He used to stay up as laaaaate as he wanted to, all the time. Every single night. Why, when he was young I think weeks went by without him sleeping. When he was young. But then the Aging got to him. Invisible, horrible creatures, that only come out at night when you're supposed to be asleep, tracked him down. They found him awake, and vulnerable. And you know what they did? They made him OLD!Aging is a cautionary tale told to naughty children. It can be any reason, it can be any source, but the point is always the same; if you misbehave, you're going to grow old. You'll start to move slower, you wont be able to run around. You won't be able to jump as high, climb as high. You'll like old people things like wine and beer, and discussing politics. Generally, these threats will be enough to scare a misbehaving child into acting more appropriately. Sometimes, examples will need to be given. Often times an older soul within Synthacrosia will play along, pretending they were once a young child within the tower, but they acted naughty, and the "Aging Fairies" got them -- or whatever source of aging they choose at the time.