because it Gives them freedom them to do things nameless or anonymous and its additionally likely that they could use it globally and also fast, controllable by themselves.
in fact bitcoin is the need of the day. and we have to accept the fact that in near future people are going to change their payment, method as some people have already changed it, therefore people are not giving preference to bitcoin instead of fiat currency.
The future is digital and bitcoin could be the leader to that, however we will not gonna enjoy our bitcoin without using fiat.
We need to use both, some people might not be able to adopt but that is alright, we are not potential for a bigger market like fiat,
we are just a payment system, it's alright to see the success.