While there is a lot lot of logic and truth in the above post, and there are many quality foods available I would disagree with a few of the comments. Live foods that come from fishless waters are not likely to harbor pathogens, particularly parasites. Most types of wild live foods (daphnia, blood worms, mosquito larvae) will come from waters that contain no fish, for obvious reasons; waters that have fish in them, won't have any meaningful quantities of live foods to collect.
When Ian Fuller, noted cory authority was over here from the UK to do a presentation for CAOC, he was very much a proponent of live food instead of manufactured foods. He was clearly not impressed with what food manufacturers offered. my own personal experience with feeding live food goes back 50 years, and continues to the present. I grow vast quantities of daphnia on the winter cover for my pool every spring. I have done this since the spring of 1995. For a period of about 6 weeks, all of my fish regardless of type or size will have live food in front of them 24/7. Mostly daphnia but also bloodworms, mosquito larvae and assorted other aquatic insect larvae. the growth rate in young fish is significantly better than with prepared foods. The reason is the sheer quantity, as live foods are about 90% water. They will also contain whatever they have eaten, which in the case of daphnia would be microrganisms and algae. Foods such as daphnia, which have an external shell, provide bulk which keeps the fish's digestive tract clean, so there is no concern about over feeding, and the "food" doesn't spoil until it dies. There is one live food I wouldn't feed under any circumstance, and that would be live tubifex. They come from very dirty places and can be full of all sorts of nasties.
As far as feeding newly hatched fry, most will do better on live BBS than golden pearls and decapsulated brine shrimp cysts, as some will die before they get the idea of eating something not alive. That is my experience, while others claim great success, and swear by them.
So, while live food isn't necessary, it should do no harm, and there are many forms which can be propogated at home where you can be assured they are safe, such as red worms, white worms, grindal worms, microworms, and daphnia. Whether you want to bother is another issue.