Q: My MP3s sound very fuzzy when I listen to them here, though they are crisp and clear from my C drive. Why is this?
A: Lo-Fi streams are of course 'Down Converted', and you lose quality for sake of smaller size. Hi-Fi is exact representation of what you upload, and when you download it is exact as well.
In order to stream files over low-speed connections, you need to shrink the size, thus losing quality. Hence, lo-fi (or lo-quality).