A full schedule is bad for a kid. They need to learn how to keep themselves entertained, or plan their own activities, or manage their own time, and they can't do that if they get a day plan from sun up to sun down.
In this age of extreme abundance, we have lost the ability to just daydream, people watch, etc. I’m not glamorizing being bored. I used to hate waiting for 30 mins for the bus.
Sorry this is something I lecture my kids about a lot! :-)