> - headphone/mic jack > - mic only jack (but why another one?) Simple: some people use headsets that have a TRRS connector (stereo audio and mono mic on one

> - headphone/mic jack > - mic only jack (but why another one?) Simple: some people use headsets that have a TRRS connector (stereo audio and mono mic on one cable), others have headsets with a TRS (stereo audio) and TS (mono for the mic) connector, while others use a separate headphone and mic (e.g. ModMic). Of course, many headsets these days use USB, but there are plenty of 3.5mm ones still floating around, and if you search "headset" on Amazon, the first two options are 3.5mm. There are, of course, adapters (TRS + TS <-> TRRS), but most people don't have one/don't want to buy one/don't know they exist. (I only have one because an old headset came with it.) It's probably only a couple cents extra to achieve much wider compatibility.