Collecting sports cards is certainly on a down slide as described in THIS recent article. I used to collect hockey cards up until college when I realized it was taking up a lot of money and space. I do however still have every card I ever collected over the years. Probably aren't going any where any time soon either. Back in 2005 I used to work at a sports memorabilia shop in the mall. I was constantly amazed how much coin people would drop on these cards.
The hobby has changed though. What started as a way for kids to learn about players and the game, not to mention build a little collection, has turned into a way for adults to make a tiny investment. The industry has changed too, creating not only run of the mill cards but making cards more valuable. Putting swatches of game used gear in a card can increase the value, many fold. Autographed cards, numbered cards, misprinted cards, etc are all on a collectors watch list. But adding value to the product has increased prices. I wasn't willing to drop 25-30$ on a single pack of cards with a chance of scoring a Sidney Crosby signed rookie card.