I remember a year or so ago that Brad Christian tried to pull the analogy of somebody liking the Mona lisa because "it's just a painting on some paper.". Which at the time made SOME sense, all though it doesn't apply to playing. The Mona-lisa isn't mass produced and in the hands of 15 year old's everywhere.
The other problem with his analogy still holds true. With something like the Mona-lisa being a painting, even people who aren't art critics can appreciate it's value. With playing cards.. Good luck trying to convince your friends that the 30 bucks you spent on cards was a good idea.
My personal opinion is this, what's the point of collecting something if nobody else is going to be able to appreciate it? Most other collectables still have some value to them and people can still understand why you collected it (depending on what it is.). Trading cards can be shown off, Baseball cards can be shown. Comic Books can be shown off and hell even your DVD collection can be shown off and appreciated on some level by most people.
Try doing that with a deck cards that might have a neat design and the chances are you'll just get laughed at.