http://www.bushfarms.com/beesqueenrearing.htmWhy rear your own queens?
Cost. A typical queen costs the beekeeper about $20 counting shipping and may cost considerably more.
Time. In an emergency you order a queen and it takes several days to make arrangements and get the queen. Often you need a queen yesterday. If you have some in mating nucs, on hand, then you already have a queen.
Availability. Often when you need a queen there are none available from suppliers. Again, if you have one on hand availability is not a problem.
AHB. Southern raised queens are more and more from Africanized Honey Bee areas. In order to keep AHB out of the North we should stop importing queens from those areas.
Acclimatized bees. It's unreasonable to expect bees bred in the deep South to winter well in the far North. Local feral stock is acclimatized to our local climate. Even breeding from commercial stock, you can breed from the ones that winter well here.
Mite and disease resistance. Tracheal mite resistance is an easy trait to breed for. Just don't treat and you'll get resistant bees. Hygienic behavior, which is helpful to avoid AFB (American Foulbrood) and other brood diseases as well as Varroa mite problems, is also easy to breed for by testing for hygienic behavior in our breeder queens. And yet hardly any queen breeders are breeding for these traits. The genetics of our queens if far too important to be left to people who don't have a stake in their success. People selling queens and bees actually make more money selling replacement queens and bees when the bees fail. Now I'm not saying they are purposely trying to raise queens that fail, but I am saying they have no financial incentive to produce queens that don't. Basically to cash in on the benefits of not treating, you need to be rearing your own queens.
Quality. Nothing is more important to success in beekeeping than the queen. The quality of your queens can often surpass that of a queen breeder. You have the time to spend to do things that a commercial breeder cannot afford to do. For instance, research has shown that a queen that is allowed to lay up until it's 21 days will be a better queen with better developed ovarioles than one that is banked sooner. A longer wait will help even more, but that first 21 days is much more critical. A commercial queen producer typically looks for eggs at two weeks and if there are any it is banked and eventually shipped. You can let yours develop better by spending more time.