Why do people invest so much?

Of course the point of investing is to make easy money back from it. That wasn't really my point. I'm more or less questioning the all or nothing attitude of some. Is there a rush to putting your whole life in? I suppose I see the point that some people can afford to lose as well, but I've also seen that people are losing things they can't afford to lose. Sure, some of it can be chalked up to stupidity, but that can't be the only driving force for some of these people doing this.