The "com" is from "commercial," which is maybe more distinct in contrast with other types of entities: "org" or "edu". Of course, that use has largely been diluted today, but it does have an inherent meaning.

How is it a poor equivalency? https://amazon is an attempt at just entering the tld without anything else and https://com is entering the tld without anything else. Just because https://amazon.com exists, doesn't mean "amazon" in and of itself means anything in the grand scheme of things.

And my point was that com alone would lead nowhere reasonable (aside from the Verisign NIC page), but Amazon by itself could very well lead to amazon's webpage.

Just like entering http://localhost or http://someotherlocalhostname works, http://amazon could as well (though with some caveats). No one has ever or would ever have any real reason to do that with com.