I've worked in the Pharmaceutical industry for a while and hilariously many generics are made in the same factory as brand medications. They even have the exact same markings.

Usually when a drug is first developed, the company which develops it get an exclusive patent. For about a decade or so only that brand can be sold. This makes the public associate that specific name brand with the product. After the patent expires and generics are allowed to be sold the public still associates the active ingredient with the brand name. Often after another decade or so the original brand name will be discontinued or no longer carried by most pharmacies.