It's been this way since the 1957 launch of Sputnik 1, which made use of two radio frequencies: 20.005 and 40.01 MHz. The United States' first satellite, Explorer 1, had beacons for the frequencies 108.00 and 108.03 MHz. Space communication nowadays borrows a huge swath of the radio spectrum for all sorts of competing purposes, from weather satellite imagery to GPS to television broadcasts.

Radio communications have some serious limitations. The radio spectrum is only one small interference-prone slice of the larger electromagnetic spectrum, and it can only offer relatively slow data rates. Unfortunately, we also seem to be stuck with it as the radio band happens to be one of only two frequency ranges capable of transmitting across Earth's atmosphere. Ultraviolet and higher frequencies are mostly absorbed, as are the infrared frequencies. We're then left with two electromagnetic "windows" representing frequency ranges that can pass between Earth and space relatively unimpeded. Radio is one, while the other is the even narrower band of visible light.