Bitcoin is connected to black market and others things heavy,that fiat were connected and still but people think they created those coin and is a ponzi thing to steal your money,besides those we may say the oldest people doesnt know work with technology soo they avoid it.The others well they dont wanna to search or know about bitcoin ,as they dont believe on it ,soo lets say that are several reasons to dont use bitcoin but is when you dont care about what may happen tomorrow for me is the same.Bitcoin has bringeg huge investors into it ,the fact it has already 7 years and a value of 400 dollars for 1 btc should make people start to search about it atleast.

Most of the people don't understand it well because of it's complex technology. They haven't ever seen anything like it before.

If we tell them it is very similar to gold than they can easily get what BTC is.

It's really the knowledge that makes us different from those who do not use bitcoin, but if they too, know that it has a value and it can be use, then one day they'll be here... 

Centuries ago salt was very hard to obtain (as gold) and therefore it's value was so high. Mean of payment have to be somehow rare to not inflate economical system with excessive supply.

yes, i am totally agree. same moment is also here in my country. no one don't know about bitcoin. what is the bitcoin? how it is works ? how it is transacting? if they will know everything about it. here this is the main reason for people not using bitcoin.