sometimes its just really hard to get them over to frozen thawed. I prefer to feed dead animals but sometimes its not really an option.
I am planning on starting my hatchlings on F/T right away in the spring. I know for breeders who have their own rodent colonies its just easier to feed live. It takes time and money to cull animals and it's just easier for them.
Personally I plan on culling and freezing or giving PK all of my snakes when I get my babies coming in..