I spent a lot years traveling and camping on motorcycles. So I always enjoyed traveling in a somewhat "basic" manner, IE: outside of the vehicle. So when I got into bicycling it seemed like a natural thing to at least start thinking about.
Then I got a drunk driving ticket and lost my license for 3 months. It seemed like a good idea to take to the bike in order to avoid the temptation of driving without a license. So off I went on my first bicycle tour. Now I'm hooked.
Probably not the best reason to start touring, but that's the way it is. I think I probably would've gotten into bicycle touring anyways, had the circumstances been different.