Are they not worth it? Are there better alternatives to prevent these cop killings than the smart gun solution?
If you can show a technology that is completely reliable under all adverse circumstances, about as close to 100% ironclad as human calculation can allow, and if it can be cheaply installed with quick failsafes in case of accidentally losing the
controlling device, then there might be an argument for using such things.
In the real world, though, matching all of the above criteria isn't going to be possible in any way, shape, or form. You would be inserting more things that could go horribly wrong in the heat of the moment.
Furthermore, that article clearly states that this type of occurrence where the officer has his firearm used against him is an exceedingly rare one, especially given that LEO's are trained in the skill of firearm retention.
"But if you look nationwide, the frequency of a police officer's gun being taken by a suspect is extremely rare."
Trying to implement "smart gun" technology is creating a horrible solution (that would cause more problems) to a problem that doesn't merit it.
After all, you don't make people (law enforcement or not) wear gas masks on a daily basis, in case of a sarin gas attack. While such incidents do occur (such as Asahara's subway attack using sarin gas), they occur so rarely, that again, it would be creating more problems than trying to solve one that is statistically not relevant.