Portable doesn't necessarily mean it needs to last as long as it takes you to hike accross a continent.

I use a laptop because I can move it from one room to another without shutting it down. While it would be nice to not have to plug it more than once a day, I'm fine with a 4-5hours autonomy.

But having more battery life definitely do not beat having functionalities such as external monitor, working internal webcam and sound.