Because whatever you think of how Musk is running Twitter it's still the most pro freedom of speech platform out there. You can hear ideas(propaganda) from almost all major players, while a UN-operated global social media would be even more censored than reddit.

The EU has their own Mastodon instance, but unless you want to have responses (even if the official instance doesn't show them), it's cheaper to run a static news aggregator.

It would be nice, but it seems most people don't care about this.

We already have the internet, anyone can make a site to aggregate all announcements from major officials.

For a more general social media, you’d have to get Russia, China, various European nations, and the US to agree on something.

why tf downvotes? What is wrong in asking an honest question?