I think if the Rust team had the capacity they might have considered adding—and maintaining—more stdlib functionality. I never asked for details but I guess that the core Rust enjoys only a fraction of the funding Go and .NET have enjoyed. It’s not only a merits based decision case I think.

Regarding C++, it’s based on a standard, the situation is a bit different. You have a variety of implementations. Imposing anything beyond the typical use case the compiler implementations have catered to would induce an insurmountable overhead on the implementation coherence. Therefore, I believe it’s more reasonable to have application-level logic in the realm of community maintained libraries. In addition, C++ is huge syntactically and the stdlib is immense, but it’s more focused on algorithmic tasks rather than on quickly building mini-servers.

Besides, the Go community has a myriad of reinvented wheels, ranging from logging over caching to maps, and until recently HTTP server libraries. The logging story for example has just recently led to a discovery of the patterns desired by the community, mature enough to accommodate structures logging in Go’s stdlib. Similarly for error handling. Robust and settled approaches turned a de facto standard make total sense to be included.

.NET is different again, having a center of gravity with Microsoft and the .NET Foundation, with typically one preferred library for a given task, contrary to Java and Go. Centralized and decentralized, the classical dichotomy.