Why are the Cryptocurrencies so popular
Cryptocurrencies are gaining popularity due to a wide variety of reasons. The foremost among those is that it makes transactions extremely simple and quick, at little to no cost. Unlike bank transactions which require fees, you could choose to use cryptocurrency to immediately pay someone in a different country even and without any transaction fees.
As an instrument of investment. As they are completely decentralized, you could theoretically store a chunk of your money in form of cryptocurrencies, and then divest them at a time of your convenience. They neither depreciate like physical assets, nor do they require any maintenance costs.
Cryptocurrencies also are expected to have a place in the upcoming IoT economy or as it is more popularly known, the machine economy. It is expected that smart machines around you will use cryptocurrencies as a means to carry out their functions without human intervention.
For example the cleaning robot in your house will place an order for floor cleaner without any interference from your side and pay via cryptocurrency.