Printed travel documents still work better than digital versions of the same documents. Physical boarding passes work more smoothly than scanning the QR code on my phone at security or at the gate. And, hard copies of e-Visas are typically accepted without question, while digital versions usually require a supervisor's approval, which takes time.
But, there's no reason that printed travel documents should be treated as more credible. The QR codes are the same and will need to be validated against a central database either way. So, as long as they check out, nothing else should matter. I can only guess that people ascribe more credibility to printed documents because they think they'd be harder to fake.
While I try to avoid printing documents as much as possible, this is a big reason why I'll continue to own a printer.