When government literally admits that we have daily sightings of UAPs they cannot explain - i do not understand why we still also say there is no evidence of alien life?
Everything about UFOs is so implausible that the alternative explanation of "we don't know what we saw, but almost certainly not a UFO" seems to be much better.
This contextualises the issue and brings up the questions you mention. Without this imposed meaning the questions go away.
People like giving meaning to the unknown.
In common parlance UFO also means "spacecraft of extraterrestrial origin", and I very obviously used it in that sense.