On Monday, May 1, 2017 at 7:12:37 PM UTC-4, ItsJoanNotJoann wrote:
On Monday, May 1, 2017 at 6:10:30 PM UTC-5, ItsJoanNotJoann wrote:

Corrected link, sorry.

https://www.amazon.com/GE-54947-Grou...words=wall+tap

Copied from OP:

"My question is why don't they make these that will
screw into a GFCI receptacle like the one in the link
instead of just plugging into the existing?"

How would you test and reset the underlying the GFCI? I guess they could
design a device that that had "plungers" or rods passed through the tap
ad operated the existing GFCI, but that sound like it would be prone to
failure/mishaps.

The do make a 5 receptacle GFCI tap to install in a standard duplex, but
I doubt that meet code since you would typically plug this into a standard
duplex which shouldn't be installed in an area where a GFCI is required.

https://www.amazon.com/Tower-Manufac.../dp/B01784Z7PI

And yes, I know that that is a plug in device, not screw-attached like the
one you linked to, another reason why I don't think it would meet code.