I know this is trite, but it is one of life’s mysteries.
I think they pump special chemicals into the air of grocery stores. How else can we explain the fact that a couple of bananas which look perfectly yellow, with even a hint of green, instantly develop brown spots and look aged when I take them out of the grocery bag at home.
Treated air. It’s the only explanation. Perhaps you have a better one?
Somber and Dull 
“‘Tis a puzzlement” about the quickly-ripening fruit; never thought of specially treated grocery store air, though. Need a good banana bread/cake recipe?–ae
Oh – and did you know? — Time flies like an arrow; fruit flies like a banana.–ae