Some contracts may need to be upheld between creator and consumer. If the consumer doesn‘t want to, well, that‘s freedom, isn’t it?
Of course it is the most code executing document format to ever execute code, so if that was the issue...
Is postscript (that‘s what PDFs are ultimately right?) capable of thing‘s that HTML+CSS+SVG isn‘t?
Edit: Oh no I completely blanked on the fact that web pages literally don‘t have pages. Seems like a big one.