Japan did it. Japan learned from the docking of the Princess cruise there and the results from each passenger. Those results were quite interesting.
And death rates by age group are revealing. The young without co-morbidities have great prospects.
September Tokyo study said, "Boston Children’s Hospital and Beth Israel Deaconess Medical School, Boston, say their study suggests that seroprevalence for SARS-CoV-2 rose to almost 50% ..."
https://www.news-medical.net/news/20200924/Tokyo-citizens-ma...
These are mainstream medical professionals from USA making findings that Tokyo is at herd immunity.
But when people suggest active seroconversion they usually mean that you start infecting otherwise healthy individuals deliberately to increase herd immunity.
So while both groups use the same word, they mean quite different things.
Who benefits from fear? I'd guess weapons companies.
Who benefits from lockdowns? No idea. Pro gamers?
I can't really decide if you're posting here to stir up a reaction or if you are strongly convinced that seroconversion is a good idea. But just for the sake of discussion, you should consider that the chance of side effects is high enough that many people would actively resist seroconversion. So my guess would be that people who consider that to be a great idea are a 5% minority. That's why governments will likely not do it.