Because, again, children's health is not accurately reflected in adult models. "Kills adults" can be correspond to almost anything in children, and telling people to bet their children's health on an unknown respiratory disease isn't good politics or good public health policy.
It's a blood/brain pathogen that is infectious via respiratory means.
A lot of the "varied issues" that long-COVID sufferers deal with are more easily explained by the disruption of the circulatory system (esp. as it affects the brain - when the body's defenses kill COVID-infected brain cells en-masse that results in the "brain fog").
Actually, a recent meta-analysis found that when you actually add a control group, most of the "long COVID" symptoms disappear. Higher quality studies were was associated with lower prevalence of almost all symptoms. "Long COVID" appears to be almost entirely an artifact of bad science (and bad science reporting)