Why would someone microwave blueberries?
Or frozen blueberries, but why would anyone buy frozen blueberries.
Because they are available and inexpensive year-round, and they defrost well and are good in many applications. Outside of the peak of local season, its the best way to buy blueberries.
Because 'fresh' blueberries out of seasons cost 3 times as much and taste like nothing much.
Smoothies.