Hey... if you're going to park your van full of miners near a charging station, why not piggyback on the wireless network from the Starbucks right there on the corner, too?
In all seriousness, owning your own hardware requires a bit more dedication than saying, "I'm going to try my luck and throw a bunch of rented hash at CK's pool." In case 1, you're limited by how much available power you've got, cooling, all the standard crap associated with running your own hardware. In case 2 it's just a few clicks.
Another benefit of the rentals is that you can drastically alter your hash rate again with only a few clicks. Considerably harder to do that when you've got your own gear.
I think I'd laugh pretty hard if I saw some guy with a large van sitting in front of a few charging stations powering a bunch of miners. Mobile data center!