What Happened to Portal Cashback for American Express Gift Cards?

Just as I was singing the praises of American Express Gift Cards due to their high rates of cashback from Shopping portals, it seems as though the cashback rates have lowered for many portals and disappeared entirely from others!

A quick check on Top Cashback and Be Frugal doesn't even list American Express Gift Cards as a partner even though they were 3% cashback two weeks ago.

Big Crumbs is now the best at a paltry 1.5%, and a few others at 1%.

What's going on?  I don't really know and I can't really get upset that they aren't giving me as much free money for almost no work, but I still hope the rates return.