If you look at it as Currency, it is difficult for an average person to understand it because it is different.
Bitcoin, being a different kind of a digital currency, it breaks down conventional thinking in many aspects. No central regulatory body. The concept of mining. The open-ledger (blockchain), the way miners are rewarded, how transporting value is determined by its packet size and not value, the hash rate, the concept of limited supply. The 100 Million pennies in a Bitcoin, etc.
Its difficult enough for people in the money space to thoroughly understand Bitcoin (we all say we understand it, but do we really?).
For a common person, its an overkill. Its like trying to explain the concept of TCP/IP, Networking, Routing, the Internet for someone who wants to use email.  Overkill.