Taste-testing on Earth is good (what else can you do?) but crewmembers' sense of taste changes in free-fall.
People who live in space have said that food is not the same in space. Some astronauts say it tastes bland when they are in orbit. Some do not like their favorite foods. Some love to eat foods they would never eat on Earth. Some crew members say they can't tell any difference. Why? NASA has some clues. But, no one is completely sure.
A Matter of Taste
So even if they liked it in the food lab, that doesn't mean it tastes good to them in free-fall.
(I believe the most-extended missions were STS-057 and STS-113, perhaps it was one of those)
Additional words about the food planning for shuttle missions (all info from Space Shuttle Food System Summary), h/t to GremlinWrangler for the suggestion
Shuttle food stowage was divided into menu food and pantry food.
- Menu food consisted of a day-by-day, preplanned rotating menu. Here's an example from STS-61C for one crewmember.
was used to accommodate individual food preferences prior to STS
41-D and also functioned as a contingency
food supply in case the flight was
During flight, this food supply was used as a pantry
providing extra beverages and snacks.
Here's the pantry food menu from the same mission
Just based on this quick look, the pantry food doesn't look less appealing than the menu food.
Also note that they did not eat the shelves bare, a tremendous amount of the food flown was returned uneaten.
28% of the Rehydratable
Food Flown in Shuttle Menus was Returned.
59% of the Rehydratable
Food Flown in Shuttle Pantries was Returned.
34% of all the Rehydratable
Food Flown on Shuttle was Returned.