The paper "Julia: Dynamism and Performance Reconciled by Design" [1] (work largely by Jan Vitek's group at North Eastern, with collaboration from Julia co-creators, myself included), has a really interesting section on multiple dispatch, comparing how different languages with support for it make use of it in practice. The takeaway is that Julia has a much higher "dispatch ratio" and "degree of dispatch" than other systems—it really does lean into multiple dispatch harder than any other language. As to why this is the case: in Julia, multiple dispatch is not opt-in, it's always-on, and it has no runtime cost, so there's no reason not to use it. Anecdotally, once you get used to using multiple dispatch everywhere, when you go back to a language without it, it feels like programming in a straight jacket.

Double dispatch feels like kind of a hack, tbh, but it is easier to implement and would certainly be an improvement over Python's awkward `__add__` and `__radd__` methods.

[1] https://janvitek.org/pubs/oopsla18b.pdf