When snapshots first launched our targets were LTS ROS distributions on LTS Ubuntu distributions.
After the 2019 security incident we used the Snapshot repository to provide a permanent home to packages that we removed from the ROS repositories since we could not rebuild them on the re-provisioned build farm and have continued the trend to provide “final” snapshots for all supported platforms.
We were publishing snapshots for non-LTS ROS 2 releases prior to Galactic mostly because my fingers are occasionally faster than my brain. We decided for Galactic to adhere to our policy of only publishing snapshots for stable LTS releases.
I wouldn’t tell anyone their use case is invalid and if I were working on hardware platforms I would want the same thing. I would still prefer that those with the need to test hardware on a fixed set of Rolling packages do so by maintaining local mirrors since I would really like to avoid people casually using snapshots of Rolling and not providing public snapshots is a very efficient, but not the only, way to do that.