At least for the dams I can answer that. The posts, if removed, are a hazard when there is a flood. You’d need extra man power/time to collect excess posts in a moment when these factors are critical in fighting against flooding. Yes, it’s not the standard to drive atop the dam, but before starting to fortify it there needs to be a measurement of how well it’s doing where.

The state requires me to. I keep them locked in a safe for most of the time.