Are there a unique use to them that can't be applied in coins that have been teammates l transacted multiple times?
Actually is quite impossible for a miner mining with GPU hardware to find a block; Unless he has a very large quantity of GPUs and free electricity it wont be feasable to use GPUs for bitcoin mining. However you can mine other coins and profit even more than mining new Bitcoins.
But answering directly to your answer, miners usualy sell most of their coins to cover expenses. even the ones who are already in profit, tend to dump some. Of course that they also hold some coins and pay for loans or simply reinvest those coins. So, if you take a look at it, most of these coins end up being dumped!