Easy,
Field goal attempts are unforced errors. No reason you can't make a field goal attempt. Stopping Brady and Gronk is a whole lot harder
FG attempts are no where near the automatic 3 points that you think they are. The snap, hold, plant and kick all have to be pretty much mistake free. Any small mistake probably results in a miss and part of the reason is the fact that the rush will probably get there a split second later. Make no mistake the defense forces plenty of missed kicks.
They make it look easy because they practice it over and over and over, but it's not.