Like photography, anyone can do a screen cast video- all they need to have is a computer installed with a screen-casting software and headphones with microphone to record their voice-Period!
So, how can you make this a business if anyone can do it? Who will pay for a such service?
If you do good job, you will probably get results which means more money. That 'more money' part is very exciting to many. But if you are not careful, it is very dangerous. Money is good. It's thrilling when you know you are getting paid to do what you love.
Now, let's say you meet a client online and he/she has the video script but is clueless on how to visualize script into a self explanatory video. Additionally, the client is not willing to appear on video or is working on a tight budget thus can't pay for a shoot. How will you advise him or her after you have looked at the script? Will you dismiss and say you cannot think of anything?