It's a hard balance to keep. On the one hand you don't want to hold back features that you know people need, but on the other hand - once something is in stable

It's a hard balance to keep. On the one hand you don't want to hold back features that you know people need, but on the other hand - once something is in stable rust the design is kind of locked in forever. It's still a fairly young language - I think it's a good thing they're being conservative with not setting too much in stone prematurely, while still having stuff released as part of nightly to see relatively widespread use. As the language matures more and more you will see less and less important features that are missing from stable.