Of all the things I've ever wanted to be different on my macbook, removable batteries have never been one of them. Now when battery life exceeds a (long) working day, why on earth would anyone want this? The very few times you will be away from a wall socket for more than 12 hours, you can just bring a power bank.
At some point Apple refuses to replace the batteries of your macbook as they stop supporting the model. At that point you could be down to a few hours of battery life, with no third party repair shop willing to work on your laptop at a reasonable price. That's where you'd be with a 2017 macbook Air for instance. Replaceable batteries gives an out to that situation, as one battery maker somewhere in the world could be…
https://www.ifixit.com/products/macbook-air-13-late-2010-201...
"with no third party repair shop willing to work on your laptop at a reasonable price."
I am not aware of any third party repair shop who would refuse to work on a 2017 MacBook Air. Unless it is a repair shop that refuses to work on Apple products in general.