At Veriff we work for the good people.
This means that we want to make sure that the person whose document is being verified is actually present and knows their document is being verified. When fighting fraud, we need to make sure that Tom isn't using his ex-girlfriend Sally's ID photo to sign her up for a service that she has no intention of signing up for. That means we have live verification sessions to make sure we can see who is submitting a session.
Additionally, there is a large number of regulations that Veriff needs to follow, and usually the quality of document photos sent via email is not just good enough to meet the regulatory requirements.