I started on string bass and trombone in the youth orchestra and took lessons from the assistant principal in the San Francisco Symphony; and then, in an effort to make myself more unemployable, I switched to guitar.
In truth, I've always had a guitar lying around. But then one day I decided to make a concerted effort to really study. Now, 20 years or so later, I've gotten to the point where I do all the band parts on the guitar behind a vocalist in the jazz and bossa style in the Tuck Andress vein (he was one of my teacher, so I took it REALLY seriously).
And yes, in various cover and original bands I get to run around like Angus Young and play Van Halen licks, which is super fun! Come to think of it, I suppose THAT'S why I switched.