I've had more than a couple friends leave they're keys in the garage, only to realize when they get to their destination that they can no longer start their car and they are miles from home, where their key is sitting. Come to think of it, one of those friends is you, isn't it?
One time, I started my car and then realized I forgot something in my house. I went back inside and left my keys on the counter. I then traveled 30 minutes away from my house to a meeting, took the meeting and went back out to my car to start it. Obviously, I couldn't because I did not have my key fob. I had to call the woman who watches my daughter to have her get my fob off of the counter and drive it to me. Keys are superior. Like mk said, fobs solve no problem I had, but they have created ones I didn't have.