Because it has a couple similarities to a Ponzi Scheme such as a referral program and you invest money expecting to earn a return. Other then that this isn't a typical Ponzi Scheme. Also, Bitconnect wants the developers to remain anonymous similar to Bitcoin. People are skeptical investing in a platform with no face... unless it's Bitcoin of course.

The differences are Bitconnect has a cryptocurrency tied to worth $300 per coin. The website does not take your Bitcoin. You transfer Bitcoin to their site and exchange it for Bitconnect coin with other users on the internet. Once you have the Bitconnnect coin you can loan it to Bitconnect and earn interest on your investment daily. Bitconnect has been paying interest everyday since March 2016. The whole idea is that your Bitconnect tokens are being lent to a software trading bot that trades the volatility of Bitcoin vs. the US dollar. Sometimes the bot has 0% days, but again it averages out to 0.9% daily. Some people think these returns are not sustainable, but again THEY DON'T GUARANTEE INTEREST. I don't think the 0.9% per day is unrealistic because I can go on Bittrex and point out coins that have went up 100%, 80%, 60%, 30% within 24 hours. So a 1% per day gain doesn't seem unreasonable to me. Bitconnect can make money even if Bitcoin goes down.