Because "He a big boy." For a while his teachers could cajole him into a diaper with the promise that he could put his underpants on top of the diaper, but then one day recently he went potty (by himself) right before naptime and shed the diaper without telling anyone. :) When he woke up, one of the teachers said, "(Gasp!) Hewitt doesn't have a diaper on!" Another one said, "He does -- I put one on him before nap." First teacher, "Well, it's gone now!" And ever since that day, Hewitt has not worn naptime diapers. :)
Attention at-home caregivers : Hewitt does still wear a diaper to sleep here. Do not let him fool you. We're not ready to try underpants on a 2-3 hour nap (versus ~1 hour at school), and certainly not overnight! What happens at your houses, though, is up to you... :)