A lot of water infrastructure is physically spread out. It be very expensive and cumbersome (and probably inefficient) to require staff to by physically present at each site for monitoring and making any changes.
I mean first you need to figure out the cost of a large municipality getting stuxnetted, and then you need to figure out where to hide when your constituents find out you made that kind of call.
That’s fine. It’s compromised. Happy with that?