Why do eCommerce giants like Amazon and Walmart don't use structured data/schema?

I didn't find any schema on Amazon's home and product pages. The same goes for Walmart (except they have Organization Schema on the home page).

Though I did find properly configured schema on eBay and Etsy's product pages. I am new to configuring schema on websites so I was wondering what could be the reasons behind it. Any info or opinion is appreciated. Thanks for your time.