Yeah, but then somebody would come and say, "when you write <i>foo</i>, what you really wanted to do is to emphasize", and so you'll write <em>foo</em> instead, and leave the italicizing out as an implementation detail.
Implementation details still have to be implemented. Someone else might come along and figure that different documents may want to interpret "emphasis" differently, and while we're at it, why not make it composable? They may design a DSL for that, and give it a cool name too, like "cascading style sheets".
Then someone else will come along and not understand it, and wonder why we don't have content, styling, and logic all in one place. He will write some script on a napkin in a coffee shop, but spill some java on it. An implementation will be made, but the spilling won't stop, not even after it reaches RAM.
I used to participate in a chat room that allowed a limited subset of HTML, and one of the tags was <marquee>. I played around with this a lot and discovered that you could nest marquees and make (very) limited ASCIImations. This culminated in someone making a ASCIImation parody of Finding Nemo. Good times.
I didn't know what that did so I googled "marquee html", they have a nice little easter egg for it. It's been a while since I've seen anything like that from google
Implementation details still have to be implemented. Someone else might come along and figure that different documents may want to interpret "emphasis" differently, and while we're at it, why not make it composable? They may design a DSL for that, and give it a cool name too, like "cascading style sheets".