Because “gaming” headphones often aren’t “just” headphones. They are headsets with a built-in boom mic

And a boom-mic is often way better than a crap wire mic or bluetooth headphone non boom mic.

There are still the trash ones, but there are also very good ones.

And a built-in mic is extremely useful on multiple situations : console gaming, tight space gaming (no place for a mic), or when there is only a single port on a device (tho a splitter, or hub could be used for a jack port or usb). There is also the convenience of just having a mic.

The issue now with all these headsets being “gaming”, is because of the marketing.

Some headphones brands have put mics on theirs, to make them headsets :

Beyerdynamic with the mx300 : the tight clamp makes it a bit of a no go for me. The mic is as just between ok and great. The voice is full, but there is a lot of noise in there from the reviews I saw.

Audio technica : they have multiple of them. Latest one the ath-m50xsts. It looks like a circum aural headset, but is not. It’s a on ear headset with eat isolation like a circum aural. Which is pretty bad for me. Tho the mic is the best I’ve ever heard on a headset.

And other brands are either extremely expensive with strange mics, or have most of their production budget into audio and they pair the headphone with a trash mic to make it a headset.

In gaming headset brands, there are multiple ones providing software, mic, and wireless features enhancing the experience of the user. For example low latency high bandwidth wireless (proprietary, wifi-like 2.4ghz) connexions only exist in gaming branded headphones/sets. (high bandwidth = higher than bluetooth for the same latency).