the chains adjust the amount of weight during your actual rep. the logic has merit because it is working your muscles a bit different on the way up and down because the weight is changing
I don't think most people need them for any reason but there is nothing wrong with trying something new. I just think it would be for a pretty advanced lifter.
Chains and bands are a great shocking method since they vary the load put on the muscles throughout the movement but unless you are an advanced lifter - they simply aren't needed.
It's only really advanced lifters who have already built a strong foundation who need to creative with advanced techniques so they keep progressing. Beginner and intermediate lifters should focus on the basics