Potential investors loses interest in investing bitcoin because the mainstream media is spreading news that bitcoin is nothing but a ponzi scheme so those with only little knowledge of bitcoin easily believes it and avoids it. Another main factor is volatility we all know that btc is very unstable currency but you can also capitalize from it unlike in the stagnant stock market.
Now there is very less media coverage. I mean in my country bitcoin is covered only when there is some major news related to crypto laws.