Because stress and panic risk causing more deaths in and of themselves.
I know the WHO is still labeling this containment phase but it is quite clear that the virus transmission is very close to being out of control. It will then spread everywhere because it spreads easily, there isn't much you can do to avoid catching it and people can be asymptomatic, have few symptoms or take up to a month to show symptoms.
To repeat, we are all getting this, sooner or later.
Prepers, sorry, but unless you can stay away from other human beings for a few months until a vaccine is developed and produced in adequate numbers so that you can get one, you are also getting it.
And yes, my DS who is 5yo is asthmatic, I have elderly relatives and a friend who is immunosuppressed. But stressing and panicking will not help them either.
We all need to keep calm. Stop raiding the supermarkets, stop freaking out and depressing the economy and we need to make sure that scarce medical resources are kept free and accessible for those who will genuinely need help because of the virus.
That is the only helpful and effective thing we can do.