Why do so few stores sell video-cameras anymore?

You need to visit camera stores that cater to professionals. Sadly, those are becoming rare. If your town has one, buy from them so they will stay in business. I'm fortunate that our town has an excellent camera store.

If your town doesn't have a good camera store, visit Adorama or B&H Photo. These companies have reputable on-line stores.

There's no real demand for them anymore. People can take videos on their phones or even their digital cameras. I have a video camera that I got about eight years ago and I used it a lot at first but stopped when I got a digital camera.

Because manufacturers like money. Selling a unit that no one is using would make them lose money. I understand your assertion, the video from a smartphone is absolute crap, but most people cannot tell the difference.

Look at the meat sold today being touted as "CHOICE" beef. The beef industry sells lesser quality beef these days to survive. They did this because of the false narrative that eating beef is bad for you. This hurt their bottom line, so either they had to raise their prices to keep themselves in business or lower their standards. They chose the latter.

Stores who stock video cameras will find them sitting on their shelves for unreasonable amounts of time. Cameras. I might add, that they had to pay money for. So, they simply don't carry them.