There can be an advantage to this if you use these for hours continuously, however, there is also a definite disadvantage.
If you hook up a good oscilloscope and compare the signals produced under load using these pads to those produced when using full copper pads and paddles, there is an obvious reduction of signal applied when using these electrodes due to their higher resistance.
It would actually be more profitable for zapper sellers to supply these electrodes because they have to be disposed of after a period of time which means more sales of expendables.
There are other alternatives though, and most zapper sellers have these other options available.