Presumably even if they don't intend to use the tld for lots of sites (perhaps stores could have subdomains) they'll be using the tld as a way of proving authenticity. Only they can create links with .amazon so they can assure customers of their safety from phishing etc.

This isn't really a good-faith argument (for Amazon or SA) because of the reliance of opinions inherent in the word "need".

It could be argued Amazon only "needs" one domain: Amazon.com (or com.amazon, heh). It could also be argued Amazon "needs" 1,000 domains (aws.amazon, books.amazon, electronics.amazon, prime.amazon, videos.amazon, etc). Who's to say who's "right" in these opinions?

Nobody really seems to care about what the most "right" domain is, anyway. Ignoring the mess that is .com/.org/.net, it's a daily occurrence to see .ai domains outside of Anguilla, .ly domains outside of Libya, etc.