Because the web is for hypertext, which means static content.
Thats what hypertext meant originally but it's evolved and moved on. The spec is literally called "HTML The Living Standard". You don't get to claim it's fixed and can't change. It just isn't.
The distinction is between growth and creep. Growth is when your spec matures to serve the original purpose even better than it used to. Creep is when your spec decides to achieve other, new purposes.
HTML has been a victim of ridiculous amounts of creep, to the detriment of growth. Creating static web content isn't really easier or cleaner now than it was in the 90s, but the protocol DOES now permit the remote end to interrogate your computer for almost as much info as the freakin' SysInternals suite.
Thats what hypertext meant originally but it's evolved and moved on. The spec is literally called "HTML The Living Standard". You don't get to claim it's fixed and can't change. It just isn't.