I can summarize the rational in one word: consistency. Do I find wines that I like in the $10 to $20 range? Absolutely. Do I purchase them year after year? Absolutely not. Why? Personally, I don't have the time or energy to scan wine magazines searching for reasonably priced high scoring wines. If I stick with high quality vineyards when I purchase a wine, even in bad vintages I am sure that the wine will still be good.
Being raised in a family that at one time made homemade wine I can vouch for the inconsistency of the wine making process. Our wines were enjoyable as the fruit of one's own labor always is. Would we have been able to sell our wines? I really don't think so. Wineries now invest millions of dollars in state of the art equipment to produce extraordinary wines. Can that really be reproduced at $3 a bottle (yes, the economy has also effected Chuck)? I think not.
This all comes to a head when I'm sitting in a restaurant, wine list in hand, and I'm at the mercy of my guests (most often my husband) to select a wine. Do I search for a recent highly rated wine or do I stay with my "consistent" favorites? I often opt for my "consistent" wines especially in off years where quality at a decent price can be found. In the end a bad good wine is always better than a good bad wine.