EME is driven by two browser vendors, Google and Microsoft, in partnership with Netflix. See Editors section of the spec,
https://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-med...
Chrome and IE are the ones pushing this - so yes, the opinion of browser makers matter, but sadly the 2 biggest ones, Google and Microsoft, do not just support EME but are the ones driving it.