Finding places to stop along the way (during the day)

What's wrong with rest areas on the interstates? Some of the better roads have rest areas about every 50 miles. If we are on a minor road where there are no rest areas sometimes we find an abandoned company parking lot to pull into or just alongside the road in a little town. The lots are not grass but better than nothing. Then, of course, there are always Walmart or Home Depot etc. parking lots.