Depending on the airline they likely can shave 1-2 minutes off the process. Doesn't sound like a lot but when you are talking large numbers of passengers the time saving can be significant.
And this means you spend less time in the queue.
As technology improves we'll have baggage tags printed at home meaning you won't even need a human to take your bag. And this will mean even more flexibility on where you drop your bag. Why schlep it from the train station to the terminal, when you can leave it at the station, or even the station you left from?