Unnecessary when there's a digital substitute, adds time to retrieve, environment. Boarding pass refreshes on the app if upgraded or seat assignments change, meaning you can avoid a gate agent interaction to swap out your paper BP. Those are just off the top of my head...

I do the iOS Wallet approach as described in the post above and have never had an issue, including in IRROPS. I have had the app BP vanish 2-3 times, I think, and the wallet BP saved me.