1. a big factor is : legal issue. it is not legal and not acceptable in all country.
2. also some people scare because bitcoin is not commodity, nor currency.
3. Prone to illegal activity
As we know due to the lack of government control, terrorists and extortionists are also utilising the cryptocurrency space to their advantage. Bitcoins users on either end of a transaction can remain relatively anonymous and cybercriminals have found ways to mask their addresses, so it can be difficult for government authorities and companies to trace such illegal activities,
other factors may include
1. Press propaganda, this is a very tough factor that hinders bitcoin, bitcoin is not press friendly and as such the press are doing all they can to make sure bitcoin does see the light of day.
2. The banking system are scared bitcoin may take the place of the banking system, the banking system are doing all they can to discoursge investors willing to invest from doing so.
3. Another factor is that bitcoin is not well publicize, the publicity of bitcoin is not well enough and as such very few people are aware of bitcoin. no one will want to invest in what he/she knows nothing about.