We think the ease of transaction provided by companies like Shapeshift and Changelly is the primary reason why most people prefer their services and not to forget their anonymity factor.
But we think that they should support more coins and stuff. Our service Click Here supports 300+ coins. Read more about our service on this blog post that compares between Changelly, Shapeshift, Evercoin and CoinSwitch
https://blog.coinswitch.co/shapeshift-vs-changelly-vs-evercoin-vs-coinswitch-e4768e43ef0c