I'm guessing they feel it validates Pinterest's growth, which they seem to talk about a lot. We recently added Pin It buttons too, not because we felt Pinteres

I'm guessing they feel it validates Pinterest's growth, which they seem to talk about a lot. We recently added Pin It buttons too, not because we felt Pinterest was an amazing way to help curate and sell product. But because people were adding our products to Pinterest quite a bit anyways and they weren't correctly tagged, attributed, or priced. So we made the decision to add the Pin It button to assist with that. Might as well if they are doing it already. I imagine Etsy saw something similar and did the same. Since doing that, nothing has really changed as far as conversions or traffic, but at least most of the images are pinned with proper data now.