OGG to MP3 bridges the open-source audio world to everything else. OGG (Vorbis or Opus) turns up in Linux apps, game audio, Wikipedia recordings and Telegram voice files — places that favour royalty-free formats — and Apple devices, many car systems and older players just shrug at it. MP3 is understood everywhere.
Convert here when an OGG you downloaded or exported needs to play on an iPhone, in a car, or in software that predates the format. Game modders pulling sound effects and anyone handling Linux-origin audio hit this constantly; the MP3 carries the same sound onto hardware that never adopted OGG.