I've seen fresh dill at Sainbury's once. Maybe you have to freeze it when you actually do find it. It doesn't seem to be around as much as some of the others. Does anyone grow herbs inside? I would think it would be too cold for them outside, but maybe I'm wrong?
Plant nerd strikes again.

The indoor environment is (usually) controlled enough to the point where human comfort = not freezing = plants will survive. The more heat and sunlight you can provide in winter, the better off they will be.
Plant respond to signals like temperature, moisture and hours of light in order to understand that it's time to do things like germinate, grow or go to sleep. Also, spring/summer is generally the time for growth while fall/winter is the time for rest.
So - depending on the plant and how it grows - if there are warm enough temps and sunlight, some plants will keep growing inside. Other plants that only put up shoots in response to a specific combination of light and temp aren't going to do anything until they get specifically what they need.
I don't know for sure, but I suspect that cilantro only grows in the spring conditions, so it doesn't make for a good winter house plant.