A drain tray or integrated dish rack is needed when a drainboard is not featured as part of the sink. It is recommended that sinks are specified that have a drain tray accessory that sits within a sink basin. Otherwise an unsightly off-the-shelf dish rack will sit on the counter directing drainage water back into the sink.
A drainboard is an area built into the sink to drain washed up dishes back into the basin. They keep the sinks free of drain trays but do take up more counter space.