Yes, that's why USB-C powerbanks exist. I can charge my laptop from one and it's nicer than lugging around laptop batteries, plus the laptop can be thinner.
Laptop being thinner is a trade off you're willing to make, I am not.
Charging a battery with another battery is extremely inefficient.
Lugging around laptop batteries is exactly the same thing as lugging around power banks, except laptop batteries don't require a dongle and a cable to tether you to a table.
Laptop batteries mean you laptop can continue to in fact work from your lap.
I am a big fan of removable batteries but even I can see the huge advantage of USB-C Powerbanks. An additional ThinkPad battery can cost ~$100 iirc. And this battery will only ever work with this specific laptop model.
A powerbank for the same price will probably have a higher capacity, and be able to charge any USB-C device.
All this is not a reason for integrated batteries, but Powerbanks using a universal interface are clearly more practical.