I think the real problem the DHS (Immigration and Secirity) has got into in the USA is it has become the employment of choice for those leaving the US military, and the personnel bring their military attitudes with them
Unused to any customer-facing approach, having had years of being barked at by their superiors it has just seeped into their lifestyle. Everything done for the convenience of those organising it. Queues just accepted without care or concern. If people miss their flights it's not their concern.
When departing US airports nowadays there are DHS notices stating their mission, including to be "professional and polite" etc to passengers. Too bad that those they employ to work within sight of these notices seem to enjoy spending their days with the opposite approach. And there is never any management around to spot it.