It’s quite easy to use media in a Blorb in a web interpreter. While external media are at a disadvantage if the browser doesn’t support the format because the interpreter might not be able to use its own codecs to handle them (particularly when running from file:.) You do have to download it all at the beginning however, so Inform’s new separated mode will be most useful for the rare case 500MB+ game. But more common is a 20MB Blorb, in which case loading it all at once is fine.
And of course the big advantage to Blorbs is not needing to do anything special for online play. You upload the one file and it can be used by people who want to download it for their desktop interpreter, or for people who want to play online.