At the supermarket, I found some frozen breaded chicken. The package said it was already fried before frozen. Why would they fry the chicken before freezing it?
To simply facilitate the end-user cooking.
You get all the "benefit" of fried food without the hassle of having to actual fry the food (hot oil handling, odors, ... )
Most people do not have fryers at home and rely on par-fried food (for example oven fries).