Niantic initially developed Pokemon Go as a lighter version of Ingress. Except that game wasn't much fun, either.
It's as if they only had a very vague concept of what it was actually like to play a single-player Pokemon game on a handheld.
BUG CATCHER wants to BATTLE!
You catch wild pokemon by walking through the tall grass, and you make yours stronger by training them against wild pokemon and other trainers. Other trainers can test your mettle by challenging you to a battle that you cannot refuse.
At launch, the only way your kids could fight with their pokemon is if you all pile into the car and drive to a nigh-random location too far away to reach on foot and fail to displace the otaku-whale that managed to put a level 500 Vaporeon on the gym with the Rattattas, Pidgeys, and Weedles that are the only things to show up in your neighborhood.
The game still needed to be both fun and playable entirely within the bounds of a single neighborhood, and it just wasn't.