On major feast days, Ethiopian Orthodox Christians may gather for worship and blessings. The Ethiopian Orthodox Church has a long and distinctive Christian tradition. Waiting for holy water, a blessing, or a communal meal belongs to a calendar of sacred occasions, not the rhythm of an ordinary shop. To understand the line, first ask why this particular day matters.
Receiving holy water is not the same as buying a product. Order and ritual may carry religious meaning. Without a record of the scene, it would be wrong to call this a simple first-come-first-served line.