It used to be that the halls had one or two congregations, and they would all fit for the Memorial in two somewhat crowded sessions-about all they had time for due to the timing of the thing.
NOW, many congregations are economizing by having 3-6 congregations (yep, I saw one with six, recently) and there is no way that all of them can fit into the hall in the time frame they consider "commanded". Even when some of the congo's are smallish, like a Cambodian or Vietnamese congo, they speak a language that can't be understood by any others in the greater community, so they can't consolidate, so the English Spanish congregations CAN consolidate and leave the halls for the minority language congregations.