You get the comfort of using react components instead of fighting with HTML tables to make your emails look nice. I think it's awesome! It's analog to what ink[0] does with CLI outputs. Sure, you could write fancy CLI outputs in bash, but ink takes the pain out of it and makes it easy.
It's also like react-pdf, where they give you react components to easily build out a PDF document without getting into the nitty gritty of the PDF spec. I'm a fan of this paradigm
[0] https://github.com/vadimdemedes/ink