I think space has a lot to do with it. Many years ago, I read an article by some researchers who had been observing wild rabbits in their natural settings. European rabbits are often found in groups, called warrens, and people have assumed from that that they are basically social. What these folks observed made them think otherwise. The strongest, nastiest rabbits lived at the center of the warren, and the most subordinate animals lived at the outer edges, where they and their offspring were most at risk of predation. Some of the lowest-ranking animals spent a lot of time just getting out of the way of the dominant animals. They saw no kinds of cooperative behavior, no mutual grooming; no evidence of "friendships" at all. Each tunnel was the sole property of the rabbit that dug it, and any other rabbit that entered that burrow would be attacked. From what they observed, the researchers concluded the the rabbits were living together because there just wasn't any other good place for them to live, and not because they preferred the company of other rabbits. We breed our domestic pets to be friendlier, more outgoing, but even the house rabbit folks will tell you that some rabbits cannot live peacefully with other rabbits, even if they have an entire human house to roam in.