I thought of using just a tablet to replace my laptop and my paper notebook, but thin client development only works with a fast, stable Internet connection.
This isn't possible everywhere. It's not even possible on German intercity trains/buses. It's also not possible across the oceans due to latency.
Even when the location is fine, there are bad wi-fi connections, paygates and network outages. Hotel wi-fi is hit or miss. Camping wifi is mostly miss. Censorship is also an issue in some countries. Some wi-fi networks block certain ports too.
My definition of anywhere includes those places, and far more remote ones. Therefore I need a local development environment, so I'm taking my laptop with me.
However, I really love the idea of working from a quiet place outdoors. I spend a few hours on my small balcony every morning. I was considering working from quiet places in the woods like you do.