Because some people were able to get rich with it, and still has prospects of making someone one even if so much time has already passed. It's not really anything new, in general most investors are like that, just not in the scale of hoping to go from rags to riches like some people hope for Bitcoin. I mean you can see it from what people choose to invest in. They choose investments that are already tested and proven to provide profit however small it may come. Otherwise they'd have invested in countless startups instead.