I do agree that it is not necessarily worth testing if you know you are sick. Just self-quarantine. I believe in actionable data. If you aren't going to do anything with the information, then the information is of little value. Meaning, if you are going to quarantine either way, knowing you have Covid or not does not really impact much at all. In fact, the information may be harmful, because it leads people to a false sense of security thinking they are now immune just because they had one variant.
However that does throw off official numbers. In the United States, 1 out of 42.7 people officially got Covid in the last 2 weeks. A lot go untested since they are asymptomatic, did an at-home test that isn't in the official numbers, don't believe in Covid, have a known exposure so why bother testing once you are sick, etc. Lets just for the sake of discussion assume half of those who got sick are officially tested. That leaves us with roughly 1 out of 20 people in the US got Covid since Christmas!