Any reasonably-well designed urban area is teeming with parks of all different shapes and types. In the suburbs, there may be one part per town, largely focused on ball fields, but in an urban area, there are parks all over the place.

The other big thing is that parks often have much better equipment than people's back yards. A lot of suburbanites buy their kids swing sets, which are usually not well designed and of poor quality. Most urban parks aimed at kids have lots of professionally-designed equipment that is well made and keeps kids attention much longer. It's also much easier to find a full-size basketball court, tennis court, etc.

You don't have to plan a trip to the park if you actually live in a walkable area. You just walk to one.