Pretty much everyone who implemented HTML5 audio for a few years, while MP3 support in the browser was initially barely heard of? Mozilla, Google, Opera, KHTML, WebKit... Safari and IE were the only outliers, and had tiny minority of market share for a while (not counting versions that didn't support HTML5 audio at all).
You couldn't use MP3 without Vorbis fallback on the Web for about a decade. Whenever you played audio in the browser without using Flash on anything else than iPhone since 2009, chances that it was Vorbis were very high for a good while. Even YouTube used it before switching to Opus.
In practice, although very popular, MP3 was nowhere near universally supported until just a few years ago. I know that pretty well - I have posted patches to some projects that enabled MP3 support once its patents expired myself.
In practice, MP3 has had support on every platform since the mid 90s. I could probably count the number of times I’ve come across an ogg file being distributed on one hand.