There's a bunch of these analytics platforms available. Government isn't the only one using them, and twitter isn't the only platform being used.

Look up Talkwalker, Hootsuite, Nexalogy, etc. Governments and other institutions use these tools.

Spreading the conversation elsewhere doesn't change the ability of these analytics platforms to cover them, although it does introduce more noise into the signal; the smaller the forum, the less an impact it has in the analytics rankings. If you slice up the pie into a ton of tiny chunks, the data received becomes less useful.

That said, some of the uses of these platforms are completely reasonable and very pro-social. We kinda want law enforcement to know if Jimmy Bullets just posted that he's gonna shoot up grade 4 English tomorrow.