In addition to cost and flexibility, Hackaday’s article explains why software defined radio is awesome and why now is a great time to get started.
First off let’s reconcile what is meant by “radio”. If it sends or receives via radio frequency it has a radio in it. This means your WiFi router, your cellphone, your laptop, many water and electrical meters, your garage door opener (but not your TV remote, that uses light), wireless security system sensors, police radios, your wireless mouse/keyboard, and that quadcopter you keep crashing in the neighbor’s yard all have one. Radios are so prolific we’re tempted to tell you they’re in absolutely everything.