A body at rest tends to remain at rest unless acted on by an outside force.

I once had over $8,000 sitting in my checking account, earning no interest whatsoever. I'd had certificates of deposit before, but at some point I got too busy to search out good local rates, parked every penny I had in checking, added money every time I got my stipend, and just ignored it for a couple of years. That certainly wasn't the worst financial blunder a college student could make in this era of easy credit, but it wasn't a logical decision. It wasn't until I wanted to buy something big and started thinking about the impact such a purchase would have on my savings that I started trying to use my money to make money.