The idea was to create a Taser system that could be effective in the intermediate range (30-100 feet) where a regular handheld Taser could not reach, but from which thrown projectiles could still be a viable threat against someone.
Ultimately, the project was a commercial failure, primarily because of the cost of the cartridges. At something like $125 each, they were nearly five times the cost of regular Taser ammunition.
I seem to remember a concern at the time being that they fired out of a traditional shotgun. In the heat of the moment there was concern that the wrong round would be used.
I believe beanbag shotguns tend to be blue or green handled/themed, and taser was aiming for dedicated yellow themed shotguns to hopefully prevent the inevitable “I thought I was using my taser shotgun when I put a real slug in their face”.