Probably more to do with FAA regulations than anything else. You can't put more than a 100W batter in a laptop, and the charger is 100W (96W, I think), but modern processors and GPUs need more than that at full speed with all cores, leave along fans and SSDs and screens. My similarly specced desktop runs at 400W, not including the monitor.
So yeah, we seem to have hit a limit with traditional chipsets. Probably why Apple is going full steam on their own ARM SoCs. The iPhones and iPads out now can do some pretty serious work, just imagine what could be achieved by bringing that power to the Mac.
The FAA has no restrictions on chargers, the restriction is on battery capacity which is irrelevant to this problem. They use 100W chargers because that's the highest allowed by the USB-PD spec, but Apple providing power supplies incapable of handling peak load on their laptops is much older than their use of USB-PD. They just seem to not care very much about the heavy sustained load use case.
I believe the frustration is more due to the fact that even though the laptop is plugged in, the battery gets drained and after a while, it will simply shut down.
I have had that issue with 2012 15 inch, 2016 15 inch, 2017 15 inch and heard similar stories from 16inch users.
Reminds me of the early brick-sized mobile phones. Sure you could be wireless, but if you wanted to use it more than few minutes, you had to find yourself a power socket.
So yeah, we seem to have hit a limit with traditional chipsets. Probably why Apple is going full steam on their own ARM SoCs. The iPhones and iPads out now can do some pretty serious work, just imagine what could be achieved by bringing that power to the Mac.