Of course ordinary citizens can use bitcoins. But, the catch is that, they will not be able to use it properly unless they have atleast some knowledge about cryptography and security. A lot of terms used in the community will leave them confused. But, the thing is that anyone can learn something if it is an interest or a necessity. Just look at computers 
Anybody can be used the bitcoin because it is digital or virtual currency, no one owns the bitcoin. No one controls the bitcoin. Decentralization is one factor that anybody uses it. We are ordinary people or citizens uses bitcoin for any transaction to earn money. I used bitcoin for my financial needs and security reasons to not take from me by the thief or in an online called hacker.