So you have two low-quality mics that can distort your discord call twice as effective.
Innovation!
As well as everyone else’s answer here about bias power: it could also just be because a 3-pin TRS are cheaper/easier to buy and get assembly tooling for than 2-pin TRS. Economies of scale.
(For a good example of this: 3-axis accelerometers are cheaper than 1-axis and 2-axis ones. Everyone wants 3-axis for mobile phones, drones, human inputs and the like. You’re better off buying a 3-axis chip and ignoring the extra channels)
I don’t think we can tell from just a picture of the plugs. These are definitely two 3.5mm stereo jacks, colored headphone and mic. Maybe have a look at the manual? Or type the model number into Google? Or use a multimeter and measure the resistance.
What do you mean by stereo wire? It’s got 3 contacts on the 3.5mm jack, that’s enough to transfer analog stereo (GND, L, R).
It has that wire to output audio on both speakers? That’s the green one btw. The pink is for mic input. USB could be for a few different things depending on the features that particularl set has.
Edit: Nvm, thought the question was for a headset, not a microphone. Unless the mic was part of a headset or something. Idk, other comments may have the answer.
