touchscreen - Why does the human skin steal field lines when it's very non-conductive in dry state?

In projected capacitative touch screens, sensors measure change in electric field coupling from the drive electrode to sense/receive electrode.

But don't field lines only terminate on conductive surfaces? This article mentions that the change in capacitance read-out when a finger is brought close to the sensor is of the order of a pico-farad. Considering how nonconductive the epidermis is (~100KOhms, worst case), this change is quite large. Wouldn't it be orders of magnitude lesser if epidermis was really acting as a sink? Could it be possible that the field lines actually terminate on conductive layers underneath the epidermis?