I have to agree with FQ on this.
It is probably pure death on squirrels and other small varmints in the same gun you carry for SD, but with all the .22 conversions available that is not an issue.
I don't see this round ever being more than a curiosity. Hang on to that barrel though as it may add to the eventual resale value of your pistol.
As to "Why ?" that I can answer.
One or more people interested in "Wildcat" cartridges were sitting around, (Possible involvement of adult beverages)
Discussing how to neck down a 20 MM casing to .17 cal when some one observed, "there is to much excess material at the neck, but I bet we could get a 9mm case to take a .22" He then went over to his work bench and said, "Hold my beer and watch this"

The short version would be "Because they could"
