Treatment on a large scale presents different concerns than on a small scale.

1. Specifically, what about reinfection? AFAIK human-to-human infection is not how toxo is spreading, and so a mass treatment plan would not affect the reinfection rate or give people any sort of immunity. So either the benefit will be temporary as people are reinfected by their cats, or this is a perpetual ongoing public health commitment on the scale of vaccinations.
2. And the treatment uses antibiotics. I suspect more lives are saved every year by antibiotics than are taken by cars, many more lives. (IIRC, there's around 50k car deaths annually in the US; I'd guess there are way more infections cured than that.) What's the risk of developing antibiotic resistance in toxo or anything people might have? (We're not risking any of the last-resort antibiotics are we?) And antibiotics aren't perfect, they can have serious side-effects.

So, I'm saying this is very far from a no-brainer on an individual basis, and it's even worse on a population level.