LTSC (or LTSB) is an Enterprise edition targeted for large organizations, minimizes non-consumer features, and commits to avoiding feature updates. It's for enterprises or embedded systems that don't want Windows changing greatly over several years of use.
Why do gamers claim LTSC is better? It's not a real gaming platform, but just ships with less "junk" than Home or Pro. You can strip Home or Pro to closer match LTSC in performance. But LTSC is also missing key features like Store app support, which must be added.
LTSC can only be purchased as a volume license, from a MS reseller or VAR. Almost everyone out there is using unlicensed copies.
Since most users have figured how to strip Pro to get similar results, there's no real advantage. And some games don't run on LTSC.