Barnes and noble wanted one of these domains and sent an appeal to ICANN. They lost the appeal.
Amazon operates these domains within a category of new domain names deemed “closed generics”, which are domain names that companies have successfully bid on or outright paid to get provisioned and own them for their own use and no one else’s. There has been persistent concern raised that this might create unfair monopolies especially for online shopping.
Amazon is the largest holder of closed generic domains on the internet. Nearly all of their domains they own are not able to be purchased and are for Amazon use only. There has been no consequences for this action and it seems unlikely there ever will for the foreseeable future as well.
There are restrictions of various types on .edu, .mil, etc. And other countries put restrictions on their TLD’s for business & tax purposes as well. Try to register a domain with something like a .au TLD and you’ll find you need to be a citizen/resident of Australia or have an actual business presence in the country.