Because there is only one Tex and many browsers. If you stick on a single browser you can perfectly control that rendering.
What about adding printing functionalitoes to surf? A non interactive mode could be used to generate a PDF for presentations. Btw in PDF happens sometimes the same that in HTML.. It's theorically print friendly but it relays on system fonts, some readers like ebooks can break the visualization, etc,.. I don't think the presentation matters more than the information contained. What is really disgusting in Tex is it's size. It gets more hard disk than openoffice and my mother can't use it. I like halibut, because it's simple and prints PDF or HTML files without library deps with decent formatting. At the end, you want only toformat the data with a template in 3 ways: presentation, paper, book formats. Is there any other interesting format? PDF and HTML are simple formats in core, but extensions have converted them In a mess ( read javascript, ..) This is the reason I wrote xml2doc, but I just did it to play, not to do the things right. I can imagine a flexible system with simple core supporting such stuff. If you need more than text and images just render the formulas as images, etc.. The system would look like Data -> format rules -> render ->output Setting columns, aligning text, placing pictures is something that matters at rendering time and must be decided in formatting time. Another simple but nice docsystem is POD. It is simple in core, in usage and the results are as they should be. It can be parsed easily and permit multiple render backends. The problem I see in text procesors is that there are many attempts to solve simple situations. But they fail at complex ones, and complex systems like Tex are that heavy that are stocked to a reduced usage by 90% of users. There is no intermediate point ctually to make everybody happy. Or at least I can't see it :)