Earthworms in potted plants?

Seems there's a tonne of differing opinions on this online, whether earthworms are a good idea for container plants or not, but I was thinking I'd at least like to try it out. I found some massive ones today. Problem is, worms always seem to die on me within minutes, and I've never understood why. I'm super gentle digging them out, then gently place them in a few inches down in the container soil. Sure, the surface layer of the soil was probably far too dry for a worm, but I figured they'd just dig downward? What I always find however is the dead bodies pretty much in the same spot I placed them. It's like they don't even try to survive. Could someone enlighten me on how to not be a serial worm murderer? Even if it turns out to be bad idea anyway, I'm still curious why this has always happened. As long as I can remember, even childhood, earthworms have always gone limp and died within just a few minutes.

Here is an article on earthworms in containers.  Maybe it has something to do with the kind of earthworms you have:

http://www.balconycontainergardening.com/wildlife/437-worms-plant-containers