They can assist with priority boarding as a visual indicator for gate staff. Seen it happen at GLA once when a gate agent directed a Silver (without looking at his BP) to the priority lane who was queuing up in the Y line.

Which brings me to something I remembered from the boarding gate for my GLA flight yesterday. The signs at the gate for cabins said First, Business, Platinum & Gold and when they made the announcement those ones were invited for priority or at their leisure and then economy boarding zones. There was no mention of Silver?? New? Sign of things to come? Skywards page still mentions Silver priority boarding.

S