Testing for Covid is relatively straightforward, swift and conclusive
When half of the country are doing it, and taking big decisions based on it (whether that be missing an appointment, through a holiday, or an operation . Or not, if they test negative), "relatively" could well mean tens of thousands of false results per day.
Not everyone may be as able, competent, fastidious, or honest as yourself.
Which renders it all a bit futile.
Then you've got the supposedly smart, who covid turned into, quite frankly, idiots.
One example:
I swim openwater.
Long story short, but I and a friend shared a car ride to go swimming.
He had been working away with a colleague the days before, sharing the driving too.
On the morning of our Saturday swim, he called me to tell me his colleague had tested positive, and that he wanted to let me know, and what I advised him to do (come swimming, or not).
I asked if he'd tested himself.
Yes, he replied, three times. As had his wife.
All negative.
So I "advised" him, that there was little point doing tests, if you were going to disregard the results anyway; that he might as well treat himself as positive until the pandemic ended, and live in blissful solitude.
He came swimming.