You have to reach a certain level of fitness before running begins to get enjoyable. Let's say your goal is to run 4 miles a day for 3 days a week. It's going to take a while starting from scratch before you can do that and longer still until it becomes comfortable, but eventually you'll be able to do it with little perceived effort. When I was doing marathons I considered running 3 or 4 miles barely worth it.

Before kids my wife and I used to run together all the time and still do when we can. Like cycling it can also be a social activity but you don't have to worry about cars honking at you because you're taking up too much of the road.

As far as transportation goes, knowing that I can run a distance if need be makes me a little less concerned about mechanical issues while riding. I always have a pair of running shoes at work and more than once I've jogged home or to the train during a snow storm when the snow got too deep for me to be able to ride. It's pretty close to a 10K between home and work.

Aside from just exercise running is a great way to reduce stress, clear your head, and energize you. There are other ways to do this of course and I'm not trying to talk anyone into anything. It is one of these thing where YMMV applies. I've had a few minor leg issues from running but I've had worse problems from cycling. Most of it has been alleviated with proper fit and technique but I still haven't completely eliminated the numbness in my left toes I sometimes get on long hard rides. Speaking of numbness, I never heard of anyone becoming impotent from running.