[Animats]

It's the open source approach to upgrading. All the cool kids are focused on version N+1, which doesn't work yet. The users still on version N don't get support any more because only losers use version N. You see this pattern frequently in open source. The Python 3 debacle spent five years in that state.

Commercial products tend to avoid this. Sales of version N go way down before version N+1 is generating revenue. Overall revenue drops during the transition. That's not good.

[steveklabnik]

Note that this isn't what's happening here; tokio is explicitly supporting "version N" in your terminology. Which is why your parent is asking why people still seem to be using the "old" version.

(Also, there's a compatibility layer, so even the people that want to play with the shiny new N + 1 can do so, even though it's not explicitly directly supported.)