... Because building them is fun?
The best part about being an engineer is developing all manner of defenses and testing them out in a number of ways. I get tired of the same ol' "rows and rows of barricades" that are so commonly built that require little imagination or creativity (as well as being absurdly expensive), so I figured trying something new and fresh would make playing engineer fun again?
besides, it isn't like they are made of concrete. They are made of the same materials as all over defenses, so it wouldn't feel "wrong" to build pillboxes as part of the FoB (and less expensive in the long wrong).
