You can. Your brand new iPhone also came with a tiny little cable that you attach to your lightning headphones and now you can plug them into your Mac. It's really not that hard.

More generally, the reasons for ditching the 3.5mm jack on the iPhone aren't really applicable to the Mac, so there's no reason to remove that jack from the Mac, which means it still has it. And the iPhone uses lightning for a lot more than just headphones, whereas if the Mac got lightning, it would literally be for just headphones. So it's really kind of a waste to add a second port on the Mac that is intended for just headphones, even though you can attempt to plug other shit into it (like a USB charger), which would be confusing, and since the Mac already has a dedicated port for headphones. Oh, and your lightning earpods came with a little adaptor that makes it work on the Mac. Also, don't forget, Apple's really trying to push wireless headphones as the future, and wireless headphones work on the Mac just like they do on the iPhone.

So it's really not that hard to see why Apple decided not to put a useless port on the Mac that would simply cause a lot of confusion down the road, seeing as there's really no reason to do that.

The list goes on and on.