Not a rustacean myself, but I think the key issue is that Python the language predates PyPI and the whole modern mentality of it being trivial to pull in lots of third party stuff, so the expectation was that the standard library needed to be "batteries included" for the language's big initial use-cases.
So part of it is that Crates has always been a first-class part of the Rust ecosystem, but the other piece is observing from Python what happens when some key functionality in the stdlib ends up completely stagnated because it can only ever add features or fix bugs with a new language release (urllib/urllib2/urllib3 vs requests, asyncio vs trio, etc). So Rust prioritizes stabilizing the kinds of interfaces and language features which allow third party functionality to plug together in a reasonable way, rather than committing to supplying all of in the core.
So part of it is that Crates has always been a first-class part of the Rust ecosystem, but the other piece is observing from Python what happens when some key functionality in the stdlib ends up completely stagnated because it can only ever add features or fix bugs with a new language release (urllib/urllib2/urllib3 vs requests, asyncio vs trio, etc). So Rust prioritizes stabilizing the kinds of interfaces and language features which allow third party functionality to plug together in a reasonable way, rather than committing to supplying all of in the core.