>>507343842 (OP)>Why do they keep doing this?I can answer that.
The cost of manufacturing x10 hollow metal poles is substantially lower than the price of x10 solid steel chain link sections.
In the olden days, people were less concerned with money and manufacturing costs and more concerned with establishing territorial dominance as quickly as possible. So chains were used.
In 2025, territorial dominance is well established, and now the priority is cost cutting, tax savings and manufacturing fences for as cheap as possible.
A cruise ship's anchor chain for example can cost upwards of $100,000 for a new anchor, with the chain itself also costing a significant amount due to its size and specialized construction. The price varies based on the chain's length, diameter, and grade of steel, but even a relatively short section can be expensive.
Rectangular or circular hollow pole fencing sections can be bought for around $4k for x100 sections and welded for free which is MUCH cheaper than using chains.
So the answer is the chains were probably either moved and used for something else or recycled for scrap.