If it isn't an immediate threat that you have to stop, why let an adversary know your capabilities (that you can detect them).
There was no overt indication that the balloons were spotted earlier.
https://www.canada.ca/en/department-national-defence/news/20...
https://www.canada.ca/en/department-national-defence/news/20...
No, the balloon was tracked when it entered Alaska on Jan 28 https://abc7news.com/where-the-chinese-surveillance-balloon-...
And there were suggestions they might also have been used elsewhere, not just in the US/Canada.
As for what intel they could collect - a payload of that size would be equivalent to an airliner full of ELINT systems, rather like the US Rivet series. So that would include possible decryption of comms, and potentially precision mapping, analysis of traffic patterns, tests of local backdoor access, and so on.
Not all of that is easily done by satellite.
Revealing that you've noticed tells the enemy about your surveillance abilities.
Not for me at least. I never claimed the military did anything (discovered it, surveilled it), just that it's possible that they could have done something without others knowing.
I just think it's extremely bad form to assume things that there's no evidence for - both about the balloon and the military, and about why people are commenting.
Regarding Occam's Razor, it's pretty simple that the military keeps secrets.
Those doods wearing dog masks in their uniform should face capital punishment.
Most of the ocean is unmonitored, too. Remember MH370? We lost it in the air and we couldn't find it in the ocean. :-)
There was an article about that very topic on HN just recently. It was not even remotely over US airspace, and the pilot had evidently threaded the needle through the radar coverage of several nations.
I also find it fascinating that these balloons were not discovered sooner, reminds me of the stray soviet era military drone that flew half of the EU without detection to crash far away from Ukraine.
Maybe the world is not under complete surveillance just yet.