Wireless headphones are a better experience is basically every way, and yes microphones on phones aren’t a niche which is why every phone has one. Totally unrelated to wired inline external microphones, though.
If you're taking a call on a phone with headphones, you need an mic on the headphones for anyone to hear you. There were several years you had the option of using BT headphones while the iPhone had both BT and the jack, but you were using the jack.
