I almost always have one printed out, but I'll sometimes have my boarding pass available in every possible form including a home printout, airport thermal, on an airline app, saved to Apple Wallet, mobile airline website (from a text message), etc.
The one thing I've noticed about most airport kiosks is that one can scan an existing boarding pass there. It might be useful to check in baggage and even print our an official receipt. I've also reprinted boarding passes in the airport stock. One time I got bored and I printed/reprinted my boarding pass 5 times. I think it was Las Vegas where they've got those kiosks at some hotels on The Strip, at the consolidated car rental facility, and obviously at the airport terminals.
Sometimes I've used one form of boarding pass at TSA and used another one to board. Nobody really cares.