Not everyone needs to typeset a full symphony with all the crazy notation for every single instrument though, having an easy responsive web presentation for even 50% of the "simple" scoring you do is a fantastic option to have.
Don't get me wrong, this is amazing work. It's likely enough for any kind of "chord and basic melody to help you remember enough to get through the gig". But for actual scoring, lilypond & friends are still the tool of choice. (I wish it was easier. I have spent way too much time trying to convince it to do the things I want :)
I'm hoping it'll get there, though.