Granted there are some cases where it is an acceptable decision to get yourself into the problem (because the advantages you gain by doing so are worth the costs). But often companies just create the problem for themselves for no good reason - they could have avoided becoming dependent on javascript to do stuff they didn't need to do in a way that broke (degraded un-gracefully) if javascript wasn't available.
You can't seriously be implying it takes more time to write functional HTML than JS. One requires the other to work, when you flip it around it's bad design.
yeah like writing basic html is so hard and more expensive than maintaining piles of js code.
You're essentially maintaining a second UI that is divorced from your main UI. There's significant cost in that. It's the same reason most sites don't support IE6 anymore.
Most sites are not gmail, they're not even close. Decoupling JS, particularly if it's done just to ensure the tiny fraction of people who disable it can use the site, can rightfully be very low on the priority list if it is a non-trivial engineering cost.