This is a reasonable point. The main benefit of this approach is that it centralizes the whole process (meaning, gives it a single Api) without making any one

This is a reasonable point. The main benefit of this approach is that it centralizes the whole process (meaning, gives it a single Api) without making any one entity dependent on another entity for business critical functionality. The issue with digital signatures is that if you're using it to verify physical goods then you have to have to store the digital signature somehow, either email it, print it out, etc and deliver it to the one who's accepting the notarized document. That person will still need to somehow get that signature, obtain the notary's public key, and verify the siganture. And if there are more than one agencies who's documents an organization accepts (think of embassies wanting notarized photocopies of passports from various countries) then that's a lot of systems you have to integrate with. This blockchain approach simplifies that without requiring all these embassies/organizations to use a service offered by a single company.