Why Quality & Why
Quality is an incredibly large concept and thus cannot be easily defined. It can be eve perceived as a philosophy (more: http://en.wikipedia.org/wiki/Quality_(philosophy).
The idea of thing's quality is very personal and often relates to the sense of aesthetics. It, of course, depends on the subject whose quality we assess. In any form of design quality will surely go in pair with aesthetics, here, we can think of a paintings, sculptures, textiles, etc. Nevertheless quality is a lot more than aesthetics. Aesthetic, to put it in simple way, means something is pleasurable to view, not exactly of hight quality, only creating such impression.
Quality applies to all things, even so trivial as books or television, in both cases we can talk about the quality of the plot/TV show subject, etc. and the way something looks (the quality of print, cover art, paper, quality of screen, etc.)
Sadly, these days, more people abandon the principle of "quality, not quantity", as we see one of the most major concepts losing its importance. It applies to both makers and purchasers.
To say quality is mostly about objects would be a huge mistake. We can also talk about quality of human relationships. As I said earlier, it's a very large concept, with a lot of different aspects.
For me, personally, it's definitely one of the most important ones. I always try to make my works have a decent quality, if not the highest possible.
Well, thank you for attention :)