Basically, if it looked interesting and/or cheap, I bought it.
When I first discovered the C & V, I simply had to have all kinds of bicycles. Well, I tried the English 3-speed and it was just to sluggish for me; even with new aluminum wheels. I turned a Raleigh Sprite into a very nice upright SS/FG but sold it to make room for my current attraction, Italian road bikes.
I've got the Pinarello and the Colnago, but what the heck is this Gardin doing here? Well, it does have that curved downtube that nobody has ever seen before and I did buy it for next to nothing, so there.
My wife's mixte singlespeed was a $25 Peugeot frame that needed a $40 seatpost to complete it. (dang French and their bizarre sizes)
Sadly, I've still got a Dave Moulton Fuso frame and a John Howard (Dave Tesch) frame waiting to be built into finished bikes.
If I stopped at a yard sale and they had a bona fide C & V bike for sale and not some Free Spirit or Varsity, I'd probably buy it regardless of what it was simply because it would be fun to fix it up to its former glory.