My family has a similar tradition of silence before meals. It provides a moment to relax and change mindset to meal time. It says that this is a time to spend together, and not just another thing to be rushed through. It's nice if everyone participates, because that provides a pause in conversation and makes it easier to stop and relax.

I think before meals is not that unlikely a time working from a blank slate. There is something powerful about sharing food. It's a bonding ritual. Using that same time to reflect and relax makes the moment of silence, grace, etc. more effective.