Workflow - Choose SMTP

Why does Workflow Management require a separate email configuration, rather than simply allowing a user to choose an existing SMTP?

Currently, a triggered Activity (email) can only be sent through a verified domain and not a third-party provider.  It defeats the purpose of routing the initial campaign through a Sendgrid/Mailgun for the Sequence, if the automated email response uses (and potentially jeopardizes) my primary domain.  

I want to use the same SMTP that was deployed in Sequences.

Thanks.