There were seemingly odd hoops for customers to jump through to have their purchases qualify for Smile. Didn't type in the 'smile' URL? Too bad, no donation for you. One of the oddest was requiring push notifications in order for mobile purchases to count ( https://news.ycombinator.com/item?id=21233815 ).
I would often forget to type "smile" when searching for stuff, but then I'd just add to cart, close the window, and go to my cart via smile. That seemed to work. But I think we can all see this for what it is — belt tightening. Will they increase other philanthropic activities to the tune of what they were previously giving away via Smile? I would be very, very surprised if so.
I suspect this is the time when the charities need smile donations the most.