In a way, playgrounds were always the same. At least, to Jack Frost, they seemed that way. They were always the same, and that was why he was always drawn to them.
Oh, yeah, he knew that some had way more stuff on them than others did. He had seen playgrounds with forts and treehouses and amazing swingsets. He had also seen playgrounds that were nothing more than a hilly piece of ground with trash.
Not every place that called itself a playground was one, though. Given what his core was, Jack knew that better than most. Some of those places that called themselves playgrounds held no fun, they had no joy or hope or wonder in them as well, so he doubted the others thought of them as playgrounds, either. They had been taken over by people who had grown up, who had stopped believing, sometimes even as children they had lost that faith younger than most.
Those playgrounds were more the domain of Pitch and others like him. Jack knew that there were other spirits out there who preyed on those who feared or worried and the like, but he thought that, maybe, they were as much a creation of the Man in the Moon as he was. So they would have as much right to live as he and the others. And while he was the Guardian who dealt with Fun for children, well....
Not everyone was children. And Jack had learned how to keep himself charged over the years. Not all of the spirits created by Manny were ones who thrived, and Jack had known immortals over the years who had simply faded away. The fact he hadn't said a lot, even if it had been a lonely existence. So Jack had learned to keep himself energized on a lot of things, and the cold had so many stories tied to it.
Still, he had always been drawn most to playgrounds. True ones, not just those places humans decided to name such. Places where children came together, over and over and over, and played. The games did not matter, as just as often, they would find Easter eggs left there after the main places had been hunted through, as Bunnymund was drawn to those places as well, and North always left little presents around, even if they weren't as obvious as his gifts in the homes. But they were gifts none the less, and Jack knew he had seen others poke around here and there. The little ones that followed Tooth around, Sandy's golden sand dusting over kids here and there as they napped in the sun.
All of the Guardians were drawn to these places. And a lot of spirits who were not Guardians as well. Such as ones like Jack, ones who were draw to these places like flowers to the sun. It fed them, gave them energy, gave them enough to keep going. For the Guardians, all the belief in them made them strong, made them able to do more to both spread that belief and to protect those who did belief in them.
In a way, it was a cycle. The more children believed in a spirit, the stronger it got, and the stronger it got, the more it could promote belief in itself. For little spirits, like Jack had been(and even if he was a Guardian now, and had a few believers, Jack was still a little spirit, with only a handful of those who believed in him), the glow from playgrounds drew them in and kept them going.
For Jack, it was easier because of the fact that you put snow down on a playground, and you were going to get a lot of happy kids throwing it at each other. Some a bit more maliciously than others, but it was fun in their mind, which is what Jack needed.
Playgrounds were special places, and the part that made a playground a playground was not the items or location, it was the children who had fun on it.
And Jack -loved- children having fun.