There are many corporate TLDs, including Amazon (took a while to be approved due to protest from the Amazon region of the world). They also have many sites on the .aws TLD.
Tip: You can search the term `site:ext` on DuckDuckGo to see sites using that domain extension (TLD). It's not very helpful for .com for example, but it's useful for queries like `site:aws` to see what sites are using the .aws TLD.
Owning your own TLD is pretty cost prohibitive. I take it that many companies simply don't have the technical skillset and have determined it isn't worth the costs.
