We have thousands of them remaining today. And usually buried in sand or in the ocean. That would be too expensive to remove because it's a blockhaus (quite sturdy) and the sand + salt ruin the tools and engines used to destroy them.

And more importantly: it's part of our history. We still keep our old castles so why not keep that. It's a good reminder too.

Here a map of more than 2000 remaining blockhaus : https://www.cestenfrance.fr/cartographie-du-mur-de-latlantique/

I thought I remember hearing that they leave some of them around just as a reminder… But I could be making that up.

They are left as a reminder of dark times. But they are also quite hard to dismantle.

What is weird about that? If there is no reason to remove it, why bother?

There is another one signed "jolie" on the other side. I think it's the writer.

If it interests you: I also saw some tags by akse ameise in flanderen and they are from Cologne in Germany