Perfectly good reason not to carry it, then. As others have pointed out, Tasers are far from universally-effective, and frankly, if the Taser is bulky and difficult to deploy, the decision to forgo it (a decision made BEFORE the encounter with the thug) may be the right one.
If the circumstances had been different, if the situation had been more controlled, if backup had already arrived, and the thug's escape pretty much cut off by a deployment of armed officers, the use of the Taser might have been a good idea, as, failing that on the part of one or more officers, others could have then shot the bugger dead.
But once the thug aggressed against the officer, the officer was duty-bound to do his best to prevent the thug's escape back into the community, and thus gave chase. Unless you'd prefer a headline like: “Thug Escapes And Murders Innocents Because Cowardly Cop Doesn't Give Chase.” The thug was an immediate danger, not just to himself, but to the entire community. He'd already proven that in the convenience store BEFORE his encounter with the officer.
This is a case where the cop actually did the right thing - giving chase - at some risk to his own safety, but in protection of the rest of the public at large.
The only reasonable choice was to plug the thug.
sitetest
It’s easy to sit here and second guess officer Wilson’s actions that day but people need to look at it from his perspective. Being in a life or death struggle with a big powerful person is stressful enough but it goes to another level when the gun is added to the struggle. He was full of adrenaline after that initial fight in the car. In his mind there was no alternative but to shoot Brown when he turned and charged him. He had every reason to think his life was in serious danger from a charging Mike Brown.