Why not? For the same reason they extended it, for the very same reason they might roll it out.
Why did they extend it? My theory is because not enough people used the promo, and they wanted to give it more of a chance.
And I'm sure, more people that used the promo more they realized that this is a bad idea.
Can you even come up with a way that Amex could make money off this? Besides if people booked standard awards.