potato_head: I was at a map where milk was plentyful and made routes to keep them supplied with grains and sent them to two cities. Unfortunately, these cities tasted the milk, and never wanted anything to do with the milk again. How do you make the milk tastier so people want it again? Adding coffee? If chocolate was around, I'd use that.
RRT2.
A known bug there from the beginning, that developers never fixed. Only way to have demand recover is to wait for "dairy processor" buildings to appear (1881 onwards).
Same problem - demand not recovering after first delivery - applies to second and subsequent items on ports' demand list, and to second items on some other buildings - steel at the cannery, for example (but steel mills do keep wanting more coal).
Being on the demand list with a value of zero still pays better than if not on the demand list at all.
Might be a user mod fix out there somewhere??