Why indeed. From a writer’s point of view, XHTML is a pain, because it’s stricter than HTML. And a few (or many, depending on whether it’s XHTML Transitional or Strict) rules changed too.
All these for what ?
However, XHTML actually does have a huge benefit (in addition to other benefits listed in the discussion above) — it makes your website viewable on mobile devices.
PDA and smartphones nowadays are no longer a rarity. From teenagers to corporate executives, they’re now have and use them on daily basis. And browse the Internet with them.
And only more of them will browse the Internet from their mobile phones.
Even here in Indonesia, I can browse the internet freely using my Nokia 9500 with flat monthly fee of just about US$ 25. And I do browse a lot from my mobile phone
You definitely don’t want to alienate these people.
Adhering to XHTML makes it easy to make your website viewable from mobile devices; actually, pretty much from any browsers. You can even change the whole layout completely in a snap, literally.
So many websites nowadays are not getting traffic from us, mobile Internet users. Their websites are beautiful in Internet Explorer, but shows utter crap or plain nothing on our smartphones.
Don’t let your website to be one of those too !