Why must a camera have a telephoto lens specifically? Maybe you meant to say "interchangeable lenses" but that would still ignore the vast majority of cameras, point-and-shoot cameras with a built-in zoom or fixed lens.

Maybe a cell phone camera would not be useful to you but I reject your snobbish assertion that a "camera" is defined by anything beyond its ability to capture and store photon information.

Btw they make lots of clamp-on lenses for iPhones et al. Some are even telephoto. I suppose it's still not a camera because it doesn't have a prism or a hot shoe or some other nonsensical thing you want to fixate on.