Ingress: Tactics—A Question of Keys

Linking and fielding are two of the best ways to gain experience points, or AP, in Ingress, and you can be quite creative and make shapes built of interconnected triangles, or just see how big a blob of triangles you can make. If you’re ambitious, you can see if you build a patchwork of your team’s colour over an entire suburb, or city… just don’t expect to do it, without some serious opposition.
But what does this have to do with keys?
Well, last year, while attempting to build Blobby (an imaginary creature made up of a network of interlinked fields), I discovered the value of the opposite team leaving keys on the ground after they’d smashed a portal. I didn’t have to hack for them; I could just pick them up and rework the links. It made building my blob of blue triangles so much quicker and faster, that I was grateful.
However, many months after my attempt to build Blobby, I’ve noticed that the opposition in my area seem to do this a lot: they’ll smash up a network of linked portals, and they’ll leave the portal keys that result, lying where they fall. Now, don’t get me wrong, I’m not complaining. I pick up a lot of keys. It’s incidental-linking Heaven!
It’s just that I can’t help but wonder why.
Pros for Leaving Keys

  • You don’ t have to spend time picking them up;
  • They don’t take up space in your inventory;
  • Another, more local, team member can come along later and pick them up and use them;

Cons for Leaving Keys

  • You can’t later recycle keys you have picked up and don’t need, if you run short of energy;
  • You can’t take advantage of keys randomly picked up to create incidental links earning more points for your team in a cycle;
  • You can’t take advantage of random keys to advance your Connector badge;
  • You can’t take advantage of random keys to gain incidental AP from links you could not have otherwise made;
  • An agent from the opposing team can pick up the keys and re-link the portals without having to take the time to hack for more keys, reducing the time available to prevent them from adding to their team’s score;

A Brief Analysis
I’m sure I’ve missed things out, like incidental fielding and Mind Controller advancement, but, even from what I have managed to list, I’m not sure why you wouldn’t take that extra couple of seconds to collect a key, even if it is to recycle it and use it for energy, or recharging another portal, or whatever.
A Note on Keys:
For those puzzled by what a ‘key’ is, in Ingress there are activities you can do involving the portals, most of which require you to be standing in the real-world location where the portal is located. Keys allow you to link one portal to another. Basically, you cannot create a link from the portal you are standing at, to a portal you can’t see, if you don’t have the key for the portal you can’t see. Each link to a portal, requires a key for that portal. Likewise, you can only recharge a portal if you are standing within 40 feet of it, OR if you have the key. If you have a portal’s key, you can recharge the portal no matter where you are. This is kinda useful, if it is attacked by an enemy agent, and you just can’t go to where the portal is, in order to recharge it. Having keys to portals is useful.