Most USA legacy carriers learned after 9-11 that if passengers are required to be at the airport too early, rather than complying many will just cut back on travel. If you make a weekly business trip, three hours early in each direction means that you're wasting about four hours every week on average, 10% of a "normal" workweek or about a month's worth of productivity over the year. Airports and airlines need to plan their staffing based on accurate predictions of anticipated numbers of customers, just like most other service industries have been doing for many decades. [For instance, any decently managed restaurant will schedule more (and sometimes more efficient) servers for Friday versus Monday night.] It's not rocket science.....and it should take the airline and airport the same amount of time to process each passenger whether the person arrives one or three hours early.