Traveling folks often deal with this, which is why I'm seeing a lot more of us switch to iPad Pros or Surface Pros instead of MacBooks. Portability and battery life are often the
only concerns when you're in airports and hotels and conference rooms and coffee shops all day. Airports and airplanes are getting better at putting power outlets in handy locations, but there still are not nearly enough to guarantee you'll be able to work.
Nearly every time I travel I'm working on a PowerPoint or some kind of documentation for an hour or two in the airport, then two hours on the plane, finishing it up at a coffee shop when I meet up with my coworkers, then presenting it for several hours at the client. None of those places are guaranteed to have power available to me.
Sure a lot of people have laptops that sit at their desk always plugged into an outlet, only running on battery when they pop into a meeting for an hour or two, but plenty more people actually need portable devices. That's the entire reason the MacBook Air was such a smash hit, you see them everywhere with both traveling businessmen and college kids, both of whom need something light and portable with amazing battery life. Both of whom are willing to forego an octo-core i7 and 32gb of RAM in exchange for 10 hours of battery life in a device that weighs less than 3 lbs.
Luckily difference devices exist for the different use cases that different people have.