Oh I know. That's the normal counter argument, and the answer is simply that sometimes I have to work off-site, sometimes in places with questionable power. And thus more battery is better, and a 10 pound brick is probably going to devote a lot of that heft to power. (But it's rare. My coworkers sometimes need to work in the middle of nowhere, though.)
With USB-C now common for power, you could power the laptop off a USB PD capable battery like this one: