In my personal life I serve HTML, CSS and native, gracefully degrading JS (if any), for the same reasons.
In my professional life though, I realised that 95% of the things I build will be changed in the next year or so. We often inherit projects that were only just finished, and our first task is to start changing it entirely.
So I aim for robustness of maintenance rather than robustness of the finished product. It's inevitable that it will change, but I can anticipate that in the same way a well engineered car can anticipate it's maintenance cycles.
On my website I have pages which date back to 1993-94. Still readable just fine. I used to post those links to mailing lists back then and they still get regular hits from people in that community because I've also maintained the URLs constant.