Is there a benefit to doing this? Is there a drawback?
If this is done when there are many people at a seuda, it could be simply to allow people to make hamotzi without waiting for everyone to wash first. Some people also do it to split up the job of cutting all the challah!
However there is a halachic angle as well, if they are being yotzei with the Baal habayis on the bracha, they would have to wait until he eats before they eat if they themselves don’t have lechem Mishnah. (So as a head of a household, people give them the honor of not having to wait for the Baal habayis)
The Shulchan Aruch in 167:15 says;
ואם הוא שבת צריך שיהא לפני המסובים לחם משנה חוץ ממה שלפני הבוצע ואז יהיו רשאים לטעום קודם הבוצע