CSS - Centering a Page

Wasn't the point of CSS that it offers standards for formatting? I naively thought the idea was to eliminate some of the pains that people felt when coding in pure HTML, specifically in regard to the appearance, formatting and layout aspects of pages. As web pages became more sophisticated over the last decade it would be logical that a more sophisticated solution was needed?

As I've begun to dabble a bit more with CSS I continue to discover browser-specific exceptions to the rules that make little sense. For instance, I have a page with a large block of content, intended to be horizontally centered. I discover though the wonders if Mozilla's IETab plugin (of course I'd never actually OPEN IE) that to do this in Mozilla, it's easy. You designate the wrapper width and set the left and right margins to auto. This makes perfect, intuitive sense. But IE shows the block left justified. Googling the topic, I quickly learned that IE and several other browsers require you to treat the content as text and set text-align=center for the page wrapper, thus creating an additional task of setting the rest of your IDs to left justify text.

Here is one page that mentions the issue and shows the solution. http://css-discuss.incutio.com/?page=CenteringBlockElement

My question....

Why?