has a lot of features and because of that features people from every field are getting benefits from so they prefer over fiat. For example the gamblers do not need to show their identity so they use only for their uses. 
Yes mate, There a wide range of feature the user of Bitcoin gets the benefits easily where Bitcoin is being used widely nor only many online sites also many public places in this world. I guess most people prefer bitcoin over fiat because It's tax free currency. There many other good reasons to use bitcoin.