If you have ever been by water and watch how it flows, you can see how different disturbances, such as throwing a rock, a duck swimming thru, even a mosquito landing, can affect the flow of the water. Water is a medium that can transfer energy and that is exactly what a sound wave is. So now imagine your room like a swimming pool, and if there are multiple disturbances, the flow of the water is very choppy and not as smooth. This is what you hear when you are recording so having an untreated room is disastrous when you try to master any type of audio.
Many mistakes new producers have is believing that they can guess what frequencies their room favors or changes by ear. You know what is going on in your room but you will never have as clean of a mix down as you would in a treated room. Believe me, I finally built a dedicated studio for mastering and the difference is night and day.
Second, proper room measurements can greatly reduce room reflections, also know as reverb. For near field monitoring, the golden acoustic ratio is not as significant. I noticed, by way of personal experience, that less bass heavy music with a few samples seem to translate pretty well, but once you get a full track with the whole spectrum of frequencies, that is when you get issues of mix down levels.