On a departure with no SID, why does ATC try to vector you to intercept the course line from the airport to the first waypoint and not vector you direct to the first waypoint, then as filed?  From  what I can tell in the real world it seems you would get vectors directly to the first waypoint, not back to the course line between the airport and the first waypoint. 

Here is my specific example:  The flight today was KBUF to KJFK.  When I turn to the heading assigned by the tower (080), but cut the turn off when I was lined up with the first waypoint and flew directly toward the first waypoint (~100), I was told I was off course and got several vectors directing  at a sharp angle (205) to the direction I was flying.  Then when I request direct to the first way point.  I get the following reply all in one long message "DELTA Twenty Six Zero One  your flight plan seems to be out of date. Please file a new one and call back for clearance. Cleared direct to Golf Echo Echo (my first waypoint)  then as filed   Expect the  ILS  approach to runway Two Two Right with the CIMBL transition  at KENNEDY  International   Altimeter is Two Niner Eight Six at BUFFALO NIAGARA  International  Contact CLEVELAND Center on One Two Five Point Eight Seven have a good morning". After that it seemed ok for a while, but then no descent clearance until I gave up and just flew my flight plan. Then much later, when I was well into my arrival, I got a message to resume navigation and climb to my cruise altitude.  I shut it off at that point.  Not a major issue, and I may not understand non-SID departure vectors, but something just doesn't seem right?   Thanks.

The program calculates a 30 degree intercept to your first leg after takeoff and tells you to turn to that heading to intercept course.

To fly it, just turn to that heading and when you get close to the track, switch from Heading mode to Nav/GPS mode and all should work out OK.

You can also increase the Allowed Course Deviation setting on the ATC Settings tab of Config to avoid the Off Course calls when you are close to the flight plan track as you describe.

It sounds like the program got confused with the DirectTo request for some reason, based on your description of that flight.

Dave