Originally posted by another user
A lot do people don't play it as much as they did when it first came
To be fair, I don't think any game could ever keep that pace considering how much people were playing it.
I played a lot when it came out the first few weeks but I've been stuck on level 16-18 for a while. For a lot of people, it's just not fun anymore. Like, once you've caught most of the Pokemon that spawn in your area, is there really much you can do besides farming the same 5 pokemon and gym battling? Gym battles are terribly boring. Farming is alright, but after a while, it just seems like a waste of time. It was fun for everyone in the beginning because you were catching Pokemon, most likely ones you had but then the excitement of a new one made it worth it to go out and look.
It would have been so much more sustainable if it was based more on the original games (catching AND battling wild pokemon, leveling your pokemon, trading). As it is though, I think their only hope is to release 2nd gen to spark that interest again.