I've seen many non-technical users, and even a few programmers, who exclusively use the caps lock for typing upper case letters. It's maddening to watch them type, but you can't argue that it's a widely-used key.
I have pointed it out to a former co-worker. He didn't seem interested in changing it. Every other time he used caps lock (i.e. several times a minute), he would leave it on and forget about it and start typing the next sentence/line of code in all caps, and then have to delete it and start over. (Of course he wasn't using an editor with a "downcase region" command.) I mainly pointed it out because every time I sat down at his computer to demonstrate something, I would get hit by this as well.
It may or may not be a coincidence that he's a "former" coworker and not a current one.
I'm one of the people that does that. While I assume it's less efficient than using shift, once you get really used to it I would argue that there isn't a big difference, and that it's not as inefficient as you think. At least for day to day use and writing code.
Try this one weird trick: rest index fingers on these raised bumps on F and J and other fingers on the keys next to them. Then when you type, hit each key with the closest finger.
Try this for some time and you will see the light ;)
