As MillerCoors and Anheuser-Busch InBev slog through another down year, executives have routinely cited bad weather and the sagging economy as reasons why consumers are buying less Miller Lite, Bud Light and other so-called premium lights.

But could it just be the taste? A new survey suggests that could be the case.

Of consumers drinking fewer big light beer brands, 27% said the main reason is "getting tired of the taste," while 21% said they were "consuming more types of other beer," according to ConsumerEdge Insights' Beverage DemandTracker, a periodic survey of U.S. adults who consume alcohol at least once a week. Economic factors, the reason so often cited by big marketers, ranked third, at 20%.

ConsumerEdge said premium lights showed signs of gradually weakening, with 30% of drinkers describing the beers as "tasting great," compared with 33% in June, 2012. Moreover, 37% of premium light beer drinkers described the segment as "watery" compared with 34% a year earlier.

What could be most concerning for big domestic beer brands is that drinkers are now more likely to name an import brand as their favorite (30%), compared with a premium light beer (28%), according to the survey. Only a year ago, 32% of consumers named a premium light beer as their top choice. Not surprisingly craft beers are continuing to gain, with 15% of consumers picking a craft as their favorite, up from 13% a year earlier.

The survey "reveals some serious warning signs for the premium light segment," said David Decker, President of Consumer Edge Insight. "After a long period when these domestic premium light brands dominated the U.S. beer industry, many beer drinkers, particularly younger ones, are finding that they prefer the stronger and more varied tastes of imports and craft beers instead. This suggests that the recent weakness in share trends for the big premium light flagship brands is likely to continue."

On Wednesday, Anheuser-Busch InBev reported that Bud Light volume sales to retailers fell by 4.7% in the second quarter in the U.S. Meanwhile, MillerCoors parent company SABMiller last week said that for the quarter ending June 30, premium light sales volume to retailers in North America fell by "high single digits," with Coors Light down mid-single digits and Miller Lite down high-single digits.

Even as they cite external factors, the brewers are racing to shift a greater chunk of their portfolios to better-performing, higher-end brands that are typically more flavorful. Anheuser-Busch InBev, for instance, has pushed Bud Light Lime Straw-Ber-Rita and Bud Light Lime Lime-A-Rita. Together the brands had a market share of 1.1% in the second quarter, the brewer said. SABMiller, meanwhile, said that its above-premium portfolio grew double digits, driven by new brands like Redd's Apple Ale and Third Shift Amber Lager, as well as strength in its Tenth and Blake unit, which includes craft-style beers like Leinenkugel's Summer Shandy and Blue Moon.

Still, these are all relatively small brands compared with the mainstream light brands, which, while declining, are still huge. Bud Light, for instance, had an 18.6% market share at the end of 2012, according to Beer Marketer's Insights, while Coors Light held an 8.7% share.

And that means the brands could have a lot further to fall if current trends continue.