There was a recent study, a blogger for the LA Times notes, that found that many parents with children enrolled in child care do not take their child outdoors daily. It's actually interesting to me that they would look at this, because as a former preschool teacher, I know that: #1: in many places it's required for children in a formal setting to go outside everyday (barring, of course, bad weather), so the children are getting outside play time and #2: for teachers, being outside is often the hour or two of the day that restores sanity, since children have the freedom to move about and be as loud as they like. So children ARE still getting that outdoor play time (perhaps not in as natural of a setting as would be ideal, but still, they are outside!), even if parents are not the instigators.
This does stress the importance of recess and outdoor play at school, which AOTA emphasizes in the article Occupational Therapy Can Help Save Recess. Recess/active play is critical for helping children to focus better, besides all of the physical benefits!