Stream realtime video between 2 computers using Python
The reason may be that you VideoCapture device is not configured for higher framerate or it does not support higher framerate at all.
You specified very low frame rate, I don't know what this means to you, but I tested it with my 2 cameras. With slightly modified code, I can max out the first camera to 15fps, but the second one is running at 25fps without problems. These are expected numbers for me.