Balloons are not that easy to detect, with no transponder and no heat signature to give them away (unlike a missile launch which sattellites can detect).
Fox reported that a Sidewinder missile was fired at one and missed, but a sidewinder is a heat-seeker, so this is not surprising. Not really that surprising that they would try to find out if they could be shot down without using a radar-guided missile. (Remember the radar signatures might be the very intelligence secret that the spy balloons were trying to discover.)
However, the big 1st one they supposedly knew about since it launched from Hainan island, China. US intelligence did not want to let it be known that they knew about it, because they wanted to study the balloon without the Chinese knowing that they knew. But the civilian guys in Montana who reported on it made it impossible for them to keep that on the D-L anymore. Once that was in the open, the cycle of balloon detecting & destroying kicked off.
Apparently they are not even sure that the balloons other than the 1st one were the intelligence gathering kind. Could be commercial. Shot them down because the policy got switched to "fuck all balloons".
Google used to use balloons for projects like trying to bring internet to remote areas, and scrapped the idea in 2021. It's not known whether they or any other company uses them for mapping purposes. Quite possible.
In any case, the Chinese government seemed interested in their balloon tech also.
Well, I do not know if this will affect military / intelligence balloons, but officials in various places are now calling for [big/high-altitude] balloons to start having transponders and file flight plans just like other aircraft. Probably for the best if that change is made.
Ditto for drones. When you think about it, drones can take many shapes, so calling these spy balloons drones is not out of the question if they are able to manuoever. An unsanctioned flight of anything these days is risky & intrusive.