I used to collect coins... not so much old ones, but foreign currency. Before the introduction of the Euro there was a huge scramble across Europe for all kinds of contemporary coins, like they were going out of style (as they were). But I never visited coin shows or traded for them, let alone pay huge amounts of money for some rare coins. Eventually I ended up leaving them in Geocaches, as it is always cool to find an old Deutsche Mark or French Franc after a successful hi-tech treasure hunt.
I'm also an avid reader, but once I finished a book I would never lug it around with me. Many times it wasn't mine in the first place, so I had to give it back. But even my own books I would give to people. So when sites like shelfari.com or even better goodreads.com came around, I HAD to add all the books I've ever read. Or at least the ones I remembered.
In the end, most of my collections are virtual, be it books, music, or steemit articles! It seems like the same fate awaits boarding passes (something I never even considered collecting), as these days all you get is a flimsy stubble, barely bigger than a cashier's receipt.