It seems to me that for the desktop view of a product detail page, it makes perfect sense to make the right column (the one containing the critical, above the fold info) sticky… assuming those critical elements don’t dip below the fold (which they shouldn’t).
Adidas does it (https://www.adidas.com/us/non-dyed-bucket-backpack/FZ6835.html) and Ikea does it too (https://www.ikea.com/us/en/p/elloven-monitor-stand-with-drawer-white-50474770/) though unsuccessfully, imo, as it is quite easy to get the CTA button below the fold, but I haven’t seen it done in many other shops and i’m wondering why? I was not able to find any data to back this up, but my gut says that the longer an “add to cart” button and is in view, the more likely it is to be clicked (assuming the overall design “works” with that layout)… but maybe I’m wrong?
I know some shops place quite a bit of detailed and marketing-heavy product info down there and maybe don’t want to detract from the allure of the pretty design or just want all that horizontal space for said design/content, but for a shop with a set of products with predictably, sparse product info who can definitely fit all of the critical info from that column above the fold (not that it wouldn’t take more than a small bit of JavaScript to detect if/when it doesn’t fit and remove the stick behavior), are there any arguments against using this approach?