I can't even tell if you're being serious with this. Bluetooth won't work for everything.
How many computers since your original IBM PC have had 3.5mm audio connectors? How many other audio devices of any kind also have had this since then and to date?
It's the universal standard for interfacing an audio source to an amplifier. It's on everything. Computers, phones, home theatre, computer speakers, TVs, cars, guitar amps, meeting rooms, auditoriums and any other venue setup, most headphones (including my wireless pair), etc...
Apple seems to want to avoid standards so they can find ways to lock users down to their "ecosystem."
On the very rare occasions when I want sound from my computers, I use speakers.
Yes, I see younger people in our office who work, or appear to be working (it's hard to know), with one or sometimes two earbuds in their ears all day long. It's hard to believe they're really focused on their work, but that's no my problem directly.
Forget headphones or earbuds, when did I ever connect my computer to an amp? For that matter, when did you connect your computer to an amp?
I'm not saying that the 3.5mm audio interface is bad or obsolete, but I am saying that in my opinion it's far, far less useful on a MacBook than a second USB-C port.
And there's nothing about USB-C that represents locking anyone into the Apple ecosphere. Even in 2015, it was just annoyingly ahead of where most of our hardware was. In 2018, it's just not a serious issue.