In the US where there is no safety net, you simply can't risk letting it be widely known because your job (& thus your health insurance) is is immediately at risk & there's no coming back from that if you're not old enough to access Medicare/Social Security
Long covid, with no known treatment, seems to be an illness where there's no upside to letting it be known you have it if you can possibly bluff your way through to continue picking up a paycheck