My daughter is a professional framer, or was. Today, it's much less expensive to out source frames from overseas. Frame shops don't have to have any tools or stacks of inventory from moldings to mattes or specialists to do the work. The frame shop she worked in has closed its frame making operation. She just started at another shop, yesterday, where she only assembles art in ready made frames. They are still custom made to the customers requests, but she doesn't operate any frame cutting equipment. Their clients are not typically retail customers, they do work for museums, artists, galleries and wholesale customers.
The former shop used several pieces of equipment since they did wood as well as metal frames, mattes, inserts, etc. For wood frames, they used an ordinary Makita chop saw. Anyone that thinks a modern miter saw isn't precise enough doesn't have enough experience with one, has the wrong blade or uses a poor technique. My daughters previous shop isn't the only one I know well. Shops have other equipment such as pneumatic frame clamps, V nail machines, crimpers and other specialty tools but a simple miter saw is pretty standard.
The issue with making picture frames is that you need to be able to cut dead on 45s and opposite frame members need to match in length exactly. Any hand operations or use of tools like miter trimmers are likely to change the length. It's very difficult to use those methods and maintain control over length. Finish carpenters installing trim in buildings would go broke if they had to do secondary operations on every one of the hundreds of miters typically involved in their daily work. A good quality miter saw along with extended fences and stops allows precise repetition. It's probably being done 100,000 times just today.
As a photographer, you might find that outsourcing frames is a great way to go. You won't have to have any special equipment or skills and you'll have access to a world of framing options you may not even know about. Of course you won't have the expense of inventory, waste or the responsibility for frames that may have issues. You can have one or 100s of frames to your exact specifications in days at far less cost than you could make them.