I hear this argument but I don't quite buy it. Since Covid we've all been pretty much checking-in before going to the airport. So if everybody is checked in who's going to get bumped? Also many airlines offer automatic check-in like SQ, AF etc. So what's the point then. Why isn't the cash that the customer handed over to the airline good enough to tell them that that customer is going to take the flight.

Sure... I agree with the advantage for when you have only a carry on... but other than that... with modern technologies... apart from enabling airlines to upsell seats etc... I'm really failing to see the point.