Still no idea what bit mining is about
If you think about mining gold, getting a fraction of it involves breaking and sifting a ton of stone. So although anyone using a spade and a hack could become a successful gold miner, the odds for finding enough to make you rich are minimal. However, it's possible to find the mother of all gold nuggets and become a millionaire in one day which was the cause of the rushes back then.
Now some people found out that there's "nuggets" as few and far between as gold in the digital world so they decided that those rarities should be worth something. Since browsing through the resources in the Internet is even easier than making a claim in Klondike it's no wonder that so many regular Joes try their luck.
And just like ordinary money isn't any longer tied to actually existing gold reserve, the value of bit money also depends on supply and demand.