[Diggsey]

Commits don't reach master until they have passed all the test suites. As such, it is very burdensome to add more test suites: it increases the time taken to run the test suite and reduces the throughput of all rust development. Not to mention, many of the tier 2 or lower targets are not easy to run in CI.

You could ask: why aren't the tier 2 tests just run before release? But then, if they are broken it may be a significant amount of work to fix, and could delay the release.

Maybe there is a middle-ground where tier 2 tests are run daily, but then you need a team of people just to fix those tests, because it will no longer be on the original PR author to make sure those tests pass before their PR is merged.