Curiosity, I suppose. No one in my family, except one uncle, smoked a pipe. He died when I was pretty young and we were not terribly close, so I don't think he was a big influence. My grandfather was a cigar smoker (El Producto Queens) and my father was a cig smoker, as were most of my aunts and uncles. My father quit cigs about 40 years ago.
I was about 19 or 20 when I picked up a pipe. I had been smoking some cigars since my junior year of high school (all of the track guys smoked cigars -- go figure!) and it just seemed like a natural extension of smoking cigars. I smoked a pipe pretty regularly through college and grad school, along with cigars and cigs. In college, I had a good friend who also smoked a pipe and we spent many hours trying all of the different OTCs (which was all that was available to us). In grad school we had a local tobacconist who was great and there was a core of grad students who liked both cigars and pipe. It was then that I discovered latakia and through grad school I mostly smoked latakia blends. After grad school, without a good tobacco shop around, I mostly smoked cigars and cigs, off and on. I tried, but did not enjoy the few OTCs I tried. This more or less overlapped the cigar boom of the 90's, so decent cigars were readily available.
Through the 90's and the 0's I mostly smoked cigars. Then, Hurricane Sandy hit and I was at home for a week (no work, no way to get to work). I had ordered cigars, but there were no deliveries and my humidor was getting light. I walked over to the local cigar store (they had power, or a generator, or something, and were open) to get some cigars. I'm not sure why, but I grabbed some Carter Hall instead. They had a dismal pipe tobacco selection -- CH, Captain Black White & Blue, and Smoker's Delight or some name like that. I cleaned the oxidation from my pipe stems and discovered that the CH was pretty good. Then I discovered on-line tobacco ordering, then this site, and I've been smoking a pipe almost exclusively for the past 4 years. I still have a cigar once in a while, but 98% of the time I have a pipe.
So, although I started with a pipe long ago, my re-introduction to the pipe is pretty much due to Hurricane Sandy.