I think only having "sort" and "stable sort" makes sense for the same reason there's only one hashmap or one vector in most standard libraries: 99% of the time you just want a high-quality implementation of one reasonable choice, without getting into the weeds of it.
Most of the time I don't care if it's timsort or quicksort, or if the hashmap uses Cuckoo hashing or buckets made of linked lists. Of course there are the 1% of cases where I notice that my sort or hashmap is a performance bottleneck and that a different algorithm might perform better. But standard libraries aren't good at serving that need because they have to be broadly applicable and conservative, if I already know that I want top performance for specific requirements I'm almost certainly better served by an external library.
Most of the time I don't care if it's timsort or quicksort, or if the hashmap uses Cuckoo hashing or buckets made of linked lists. Of course there are the 1% of cases where I notice that my sort or hashmap is a performance bottleneck and that a different algorithm might perform better. But standard libraries aren't good at serving that need because they have to be broadly applicable and conservative, if I already know that I want top performance for specific requirements I'm almost certainly better served by an external library.