I know tons of people that are 30-something and are out and about during the day. Most still work full time or close to it, many earning $100k+ salaries.
One neighbor is a programmer and works from home for a silicon valley firm, and I see him out late into the morning and sometimes in the afternoon going out for a jog. He's able to volunteer at our kid's school whenever he wants (my kid is a classmate of his kid). I think he's full time, but very flexible.
Another friend in the neighborhood works from 10 to 7 pm at a firm on the edge of the neighborhood. So he's free in the mornings, and normally takes a late lunch around 2-3 pm so he's out walking to/from school to get his kid many days of the week. His commute is about 1-2 minutes (maybe 3 if he bikes) so popping home for lunch is no problem.
Another friend with six figure income works 12 hour rotating shifts and is off for 3 to 6 days at a time, so we'll hang out at my house in the middle of the week (when his wife is working). He's also not working during the day half the time (works at night often), so he probably goes grocery shopping and runs errands during the week in the middle of the day after a shift.
That same friend's wife (attorney, six figure income) works Monday through Thursday (officially) at an 80% schedule and takes Friday off (when she can).
Another friend working in the pharma factory doing QA/QC (biochem stuff) works Sun-Thurs and is off Fri and Saturday. We hang out occasionally on Fridays with him, his wife and kids and my kids.
Another friend in the neighborhood is law enforcement and rotates day shift and night shift. So he's free during the weekdays all day half of the time.
Another friend in the neighborhood works from home most of the time doing TV station stuff (graphics, coordination, programming).
Another friend in the neighborhood does shift work at the grocery store and is home during the week half of the time.
Many other friends/neighbors work from home or "work from home" (artists, musicians, architects, landlords) and are out and about during the day.
All of these people (save the 50-something year old architect) are 30- and 40-somethings.
Come to think of it, I don't really know that many people that have straight 9 to 5 type jobs (other than former coworkers when I worked at a 9 to 5 job). They obviously exist (see, for example, rush hours that occur every day around 7-8 am and again 5-6 pm). I may have also self-selected myself into friendships with non-traditional people.