There are several reasons why it's not a legit currency. For one bitcoin isn't accepted at every store you go or every online website you order stuff from. And on top of that the price fluctuates so much that if you buy say a cup of coffee for 1 bitcoin by the end of the day that coffee should have been 2 bitcoins. There isn't a set number of value of an item. It changes by the night. It's store of value is just not stable.