Earlier quoted context omitted.
95% of the functionality web apps I've been put in charge of building works without JavaScript. You do lose things like form validation, and some of the links to things like detail forms opens in the same window instead. Or, say, a master/detail selection having a full list of hundreds of items instead of 90% of them hidden based on It's useful for most of the reasons listed in the parent article. You can also do qui…
HTML and CSS have form validation too. You can do something like :has(:valid) when you add in your validation schema in the HTML.
I am a fan of the HTML5 validation though - offered feedback when they were working on it that I think made it into the spec like interaction of required and hidden elements...
And, I suspect for most of our forms the simple patterns of HTML5 validation would be fine, it's just that sometimes it wasn't, and it was easier to be consistent in how validation worked and looked... So. Chalk it up to laziness. So long as the forms still worked we decided to let it be.