Not everyone is concerned with profit. It's a legitimate point for those that are.
I do this for the enjoyment and challenge. Video presents some significant downsides in that regard. First, it's difficult to avoid telling the same story with video when you are vacation shooting. Second, you won't know your footage until you've shot it so you won't know if you gotten your glue shots until it's too late. Third, video has a tremendous amount of post that's critical to the presentation and occurs entirely after the dive or trip. Fourth, once your work is done it can be difficult for you to enjoy and difficult to share, plus many won't want to invest the time to see the results. Unlike a still, you can't choose to look at a video "real quick". Sharing video on the net is possible now but it's still more challenging than still. I used to post videos here when I shot video, but I don't think many people ever viewed a video I showed on Wetpixel. They'll look at an image of mine or yours because it doesn't demand five minutes of their time.
It all boils down to the fact that video stresses me out on a trip whereas still is just great fun. I respect that video is, in many ways, as hard or harder to do well than still. I consider video a format for others' enjoyment and still a format for me. If I were a pro I'd be into video.