When dealing with audio, a certain accuracy is required, and a possible approach is supersampling. In the decimation, it is likely that some averaging is done to increase the accuracy of the reading. The hardware required for the ADC conversion is also simpler that way.
The extreme of this approach are sigma-delta ADCs, where just a comparator is used to sample at a single-bit accuracy with a lot of supersampling, and then some clever logic is used to reconstruct the signal. The advantage of this approach is that, in short, linearity is much better and easier to achieve.
Besides, while it's true that Nyquist frequency is twice the maximum frequency of the sampled signal, in order to get usable values you need to go farther than that. More likely 5-10 times the maximum frequency.
I've learned recently that lower frequency radio waves travel farther and have better object penetration than their higher frequency counterparts.
Then you learned poorly. This is simply not correct. Different frequencies go thru different materials differently, but it is not true that lower frequencies (longer wavelengths) "travel farther" somehow.
Think of really high frequencies, like light. Here we can discern different wavelength with our bare eyes as colors. Surely you must realize that red light doesn't always "travel farther" than blue light.
What does happen is different wavelength react differently to different size objects that they can't go thru. There are three basic effects going on, reflection, absorption, and diffraction.
How much a certain material absorbs EM radiation is very material-dependent, and often not monotonic with wavelength. Think of color filters. A green filter blocks both red and blue light but lets green light thru, even though its wavelength is between red and blue.
Big things relative to the wavelength will block the radiation. However, waves also diffract along the edges of objects. This is sortof a wave bending along to follow the object. This happens only along a thin layer near the object, with the thickness of this layer proportional to the wavelength. Long waves, like 1 MHz commercial AM can bend around the edges of hills and the curvature of the earth better on a human scale than 100 MHz commercial FM, for example. This may give the impression that these longer waves "go further", but that's not what's going on.
Short wavelength don't bend around the same object as well as long wavelengths, but they can slip thru smaller holes in objects or between objects. Again, this is proportional to wavelength. A 10 m hole will easily let 3 m (100 MHz) signals thru, but mostly block 300 m (1 MHz) signals. This is probably why the shorter wavelengths work better between decks of a ship. They bounce around better and eventually make their way thru doors and the like, which longer wavelengths can't.
Best Answer
In free space, it doesn't matter. The power per incident area of a propagating wave is inversely proportional to the square of the distance from the transmitter. This is true regardless of frequency.
Certain frequencies are reflected, refracted, absorbed, and scattered differently by different materials. There is no single monotonic relationship until you get to really high energies, like gamma rays and beyond. At these really high energies (high frequencies), the waves basically just blast thru any material in their way, with higher energies passing thru material with less attenutation. Up to below Xray frequencies, there is no single answer, and it depends on the material between the transmitter and receiver.
Diffraction effects can make low fequencies (long wavelengths) appear to bend around objects, but this actually occurs at all wavelengths. The "near" layer where diffraction effects occur scales with wavelength, so it appears to us at a fixed human scale that long wavelengths go "around" objects where short wavelengths don't, but that is due to our perception scale. On the scale of the earth, commercial AM radio frequencies around 1 MHz are low enough to diffract around the curvature of the earth to some extent making over the horizon AM reception possible. Commercial FM radio, being 100x shorter wavelength, exhibits this effect much less for the same size earth, so FM radio appears to us to be mostly occluded by the horizon.