Why is it impossible to change content in css?

Question

CSS2.1 pseudo-selectors such as ::after and ::before allows to add text content to the page. For example :

CSS

Answer 1

As specified by the spec content: is only usable together with the *pseudo-elements :before and :after, there isn't a better answer than that I'm afraid.

12.2 The 'content' property

This property is used with the :before and :after pseudo-elements to generate content in a document.

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However, if the question should be interpreted as why aren't we allowed to add content anywhere we like using CSS? The answer is only theoretical but as simple:

CSS is not meant to be a way to provide new content, it is a way to format existing such.

"You are not supposed to change any content using CSS, there is not that much more than that to it. The :before and :after pseudo-elements have been discussed quite frequently because they break the barrier between formatting and content." - refp

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:before/:after are a great resources because they allow you to format your data in a way that wasn't possible before their appearance. Notice that I use the word "format" because I still consider it to be a formatter, not a data generator.

Coming up with a usable alternative that would still have a clear line between formatting and content would've been very hard (and frustrating), so this is (at least according to me) an acceptable middle-way which I can live it.

_{I must admit that I wasn't a big fan of the pseudo-elements in question when they first appeared.}