OK.
Telecommunications can encompass a great variety of frequencies depending on the type of data being transmitted.
But I'll discuss audio transmitted upon a carrier.
When a broadcaster speaks into a microphone or when an audio recording track is to be transmitted via a medium such as radio, it must be modulated, or superimposed, upon an appropriate radio frequency carrier. The choice of frequency and modulation scheme may be dependent upon the circumstance of the recieving "station". Some modulation types and frequencies are good for long distance, some better for faster data transfer, some better for local communication, some better for audio/video/data together, and some better for digital links etc.
But in the case of transmitting audio signals through radio, audio "baseband" is too low frequency to be transmitted via electronic means. It is subject distortion and interference. For radio transmissions, well it is outside of the frequency range that is effective for radio. We are talking about frequencies in the hundreds to low thousands of Hz. I think the AF threshold is considered 20,000 cycles/second.
We do transmit AF, when we speak! Or when we hear we recieve it.
Modulating gives us the ability to tranmit audio over long distances via the advantages of radio frequencies!
And your last question about waves fading out. Well, indeed in a manner of speaking modulation reduces the rate of fading out of a signal, but only in the sense that audio waves do not travel very far on their own, and radio gives the advantage of long distance wave propogation.
Do you understand how AF is modulated/demodulated, the AF, IF, and RF, and filtering stages of an amplifier and reciever, etc?