Why do the majority of internet users live in districts with late cutoffs?

According to this website, https://www.cga.ct.gov/2000/rpt/2000-R-1188.htm, most states require a child to turn 5 before October in order to start Kindergarten. However, every time I see a redshirting discussion, the majority of the people commenting claim to live in districts with cutoffs in October or later, even though that's not the majority of states. Is there a reason for this? What's the cutoff in your district and if it's after September, what percent of October children are held back?