Why is this? According to a post on Reddit, it has been discovered that running Ingress and Pokemon GO at the same time will allow gamers to discover hidden Pokemon much more easily, which in turn could lead to the discovery of rare Pokemon. Of course discovering rares is possible the regular way, but if you’re looking to get that leg up on your friends, this is a pretty neat trick.
So how does this work? Basically Ingress will show on its map white dots which mark energy hotspots. It seems that there is some correlation between these hotspots and Pokemon, where the more hotspots there are in the area, the more likely there will be Pokemon that can be discovered.
However the only drawback to this methodology is that both games will be huge battery drainers. As it stands, Pokemon GO is already draining a lot of batteries so you can only imagine the drain if you were to launch Ingress as well. However if you are super hardcore about catching rare Pokemon, better bring along a power bank or two.