You're arguing over 58 bytes. If someone just wants a minimalistic page, setting a centered body with max-width is step 1. If you stop after step 1, cool. If not: your page is probably going to look better.

However, there is a marked difference between "the content is centered in the browser with whitespace on the sides" and the browser default "it's on the left with all the whitespace on the right". The first one wins. That _should_ have been the browser default in absence of a stylesheet rel, but CSS was born when screens were majestically tiny and the idea of a 24" widescreen was literally a vapourware joke, so it wasn't, and so it never will.

Default browser styling sucks tremendously for mobile browsers.