For me, what is important about a park is just getting out of the house and enjoying nature. When outside, we can enjoy the sounds of birds, trees moving, and people enjoying themselves outside, too. A park is a place where people can just take a breath and enjoy a nice walk or sit in the grass and get away from the world.
During my summer trip in NYC, a group had
over the city for people to just sit
down and play. It didn't matter that there was a random piano out in the open, people came up to it and either played the piano or listened to someone playing along.
Along with playing, just getting to use the resources in parks to play around is nice. There was this park in the Chinatown in Manhattan where, not only were there swings, but the open grass area was where a lot of people went out to play badminton.