It is recommended everywhere because it is useful, not because people are 'parroting this stuff'. I think any real critical review of the data would conclude with a suggestion that bulk bottled water is a good idea for people to stock up on.
> Do these people think coronavirus is going to cause enough unrest to destabilize civic services and affect our municipal water supplies?
No, I don't think anyone is worried about that. This is the first suggestion of that nature I've seen, I think you are arguing a straw man here. The primary reason for bottled water is to help prevent the spread of germs by reducing shared water sources. A secondary reason would be general risk-reduction: having your own clean safe water is a calming factor and reduces/eliminates at least a few possible contamination sources.
It is a logical move, not some hare-brained silly idea that people are 'parroting'.