This is a popular trend in some communities, but not in others. Here in the Bay area, it's quite common, especially for boys. Part of that has to do with the fact that the kindergarten curriculum has changed dramatically since most parents went to school. For the most part, kindergarten is not just a time to play in the sandbox and finger paint. Now many kids learn to read and write in kindergarten, skills that used to be taught primarily in first grade. Especially for boys, who tend to develop fine motor (small hand) skills needed for writing later than girls, authors like Michael Gurion and others have advocated the idea that parents wait until boys are 6. Here are two great places to start to learn more:
And wouldn't it be nice to have the luxuary of simply having this as a choice instead of needing to send our children to school to save on a few hours of childcare cost.
Our system of education and childcare for the working (poor) has to change and likely to only happened by us, the families and parents. We can no longer wait for the powers who are so out of touch.
To the point of the question, my son benefitted greatly from starting kindergarten late. But I think there is too much emphasis on education too early. Kids need to be kids and to share that experience with other children first!
When parents ask me I always suggest they hold off if the child is a young 5. I think the demands that kindergarten now places on children is just to intense for that age. Give them time to play school will come soon enough.