XHTML1 depends on DTD for entities, which means that parser must fetch DTD from w3.org (from heavily-hammered server) or support DTD catalog and have one set up in the system (rarely available out of the box, not always possible to do). IMHO that breaks "works everywhere out-of-the-box" promise, and sometimes it makes it easier to just use HTML parser.
It's been 11 years since XHTML recommendation was published, and you still can't rely on XML parser for reading content on the web. Even documents labelled as "XHTML" are often ill-formed (and almost all of them are sent as text/html). Even if we were moving in the right direction, we were moving too slowly. Now that HTML5 parser is specced, it may be quicker to add it to popular languages than turning whole web around.
I agree that the DTD issue is a nuisance but it's a nuisance that can be solved in a few hours. XHTML has not solved all parsing problems but the quality of parsing results is infinitely better than it used to be a few years back because most websites do actually use well-formed XML (at least most of the ones I'm parsing).
I don't understand why we need yet another slightly incompatible pointy bracket syntax. Adding that syntax to all languages and ironing out all the quirks will take years and it won't replace the existing mess. It will just add to it. I see no progress at all. It's a pointless waste of resources.
I'd say that being able to parse XHTML isn't any easier than parsing HTML in that both requires an author who writes strict code. There's HTML strict, too, ya know.
It's been 11 years since XHTML recommendation was published, and you still can't rely on XML parser for reading content on the web. Even documents labelled as "XHTML" are often ill-formed (and almost all of them are sent as text/html). Even if we were moving in the right direction, we were moving too slowly. Now that HTML5 parser is specced, it may be quicker to add it to popular languages than turning whole web around.