Why use class CL_BCS for sending emails?

For years, I've written many programs that use SO_DOCUMENT_SEND_API1 to send emails, with attachments.

Now SAP tells us to use CL_BCS???

What are the advantages of using CL_BCS?

To me it just seems like a more difficult way to do the same thing?

Or am I missing something?

What's wrong with just using SO_DOCUMENT_SEND_API1?