rust port dep license need?

it seem only rust crate need license info. go and other ecosystem do
not. is there a reason only this needed for rust? it seem to add
complexity, time, and effort since it multiple to step to make crate
list and then add license. maybe could be one step?

couldnt find on list but maybe used wrong terms.
https://man.openbsd.org/cargo-module.5 docs also lacks the info

thanks in advance