Tasers are routinely used to attempt to deescalate situations.
The problem is though they just aren't terrible effective and often fail. Simply wearing thick clothing can't prevent penetration, distance and wind can prevent them from even making contact, batteries age, etc. An enraged suspect, such as one on drugs or drunk, can also rip them out of their skin or outright not be deterred.
Here's one study that backs up what I've said above
> A total of 2,395 use-of-force reports indicated conflict ended at the first “iteration” (the officers’ first application of force). In the first iteration, TASER’s were deployed 2,113 times. Out of these deployments, 1,459 ended the conflict at the first TASER application (69-percent success rate); chemical agents had a 65-percent success rate; impact weapons had a 45-percent success rate at the first iteration; takedown had a 42-percent success rate; and compliance holds had a 16-percent success rate.
https://www.ncjrs.gov/App/Publications/abstract.aspx?ID=2460...
69% on the first attempt, when the officer's life is potentially in risk (and anyone else at the scene), is a pretty lousy success rate.
You can find more data (just be vigilant as the manufacturers like to muddy the waters with their own claims) if you'd wish to continue looking.