I think the only difference is whether something is officially supported or not. When it is officially supported, it tends to not break and has to run through a bunch of tests that ensure that std lib doesn't break with every programming language release. It tightly couples them. With off the shelf libraries, there is always a delay.

I also have an ideological take - I think of programming languages as a tool box and like a car mechanic, you want to have dependable tools that are robust, don't break and has good support. Basic algorithms and datastructures should always be included in the programming language - this is subjective but I firmly believe in it.