But, because if we don't do something to slow the spread of the virus, it will overwhelm our healthcare system, and in turn, have severe consequences, not just for COVID-19 victims, but also for everyone who need hospital care.
There actually is not a lot of good evidence that the forced isolation is going to help healthcare outcomes, at least in the US. There are several academic studies which suggest it will not be sufficient and may actually make things worse in the fall if SARS Cov-2 has moderate seasonality (which is presently unknown).
This was the initial theory and suggestion by people like Dr. Fauci based on incomplete data. But what these assessments have generally not balanced is the costs of the interventions, either in terms of unintended deaths due to things like suicide from increased isolation or economic depression. Epidemiologists tend to be focused narrowly on preventing the spread of disease, not necessarily on cost-benefit analysis. Economists have done a better job of looking at these costs so far.
One way to look at this, noted by a colleague today, is that policy makers have chosen to undertake the largest and most expensive public health intervention experiment in the history of mankind. Using tax dollars no less. Scientifically, I think people will be finding all sorts of weird unintended effects from these interventions for several years. Particularly if the forced isolations are turned off abruptly it should be easier to recognize these weird blips in responses.