Money is a very strong incentive to get involved with things. If it wasn't for the stories about enormous gains over a relatively small time frame, bitcoin wouldn't have received that much exposure. That's also the reason why those coins that are directly backed by the USD 1:1 are going to fail.
People are hoping to have similar outsized gains in the price of bitcoin when they invest/speculate in bitcoin.
The main reason people want to use bitcoin is because it is more cost effective then alternative payment methods.