Do you prefer white wine or red? Collect HO or N gauge railway models? Do you prefer actively managed funds or index funds? Stocks, Bonds or Property?
I must admit that to a large degree I treat investing as a hobby. I enjoy reading through the weekly investment lift-outs in the newspapers, read investment magazines and surf the web looking for the next "millionaire in the making" article. Even if a lot of it doesn't teach me anything new, or I don't agree with the viewpoint, I still enjoy spending my time "playing" with my investments and reading about investing. Just as I enjoy reading about scuba diving sites or model railway layouts. Sometimes I'll even open up a new investment just for the fun of it.
Another thing in common with my other hobbies is that to some extent I accumulate net worth just for the sake of it. My retirement fund is on track to support me when I choose (or are forced) to stop working for an income, and although my other investments have theoretical performance targets, and target amounts, I'm not saving for any particular items or expenditures.
For me, saving and investing my money isn't all about deferred expenditure for some future purchase. For me the act of investing is an "experience" or "consumption" in and of itself. The only strange thing about this particular hobby is that often the more you spend on buying fancy new investments, the more you can afford to indulge your hobby in the future!
One mildly worrying thing (OK, it doesn't actually worry me at all) is that many people apparently view collecting money as a hobby as an undesirable behaviour. While gathering money to "keep score" may be OK for businessmen (ie. investing as a sport), it is viewed as unwholesome to accumulate money "for it's own sake". Some people continue to have a phobia about being poor even when they are, by most measures, already rich, and thus end up taking frugality to extremes and becoming the stereotypical Scrooge McDuck. I'm sure many well-balanced people enjoy the simple pleasure of watching their net worth increase over time. And you don't have to justify it by saying that you're saving for that round the whole cruise you've always wanted, or intend leaving your millions to a charity in your will.