It's a common theme that most people score worse in a tournament than they would in a casual round for a variety of reasons. Whether it be pressure, harder courses, or having to play in a 7:00 shotgun, there is something that prevents most from shooting their handicaps in tournaments. In many cases courses will ramp up the green speeds the morning of and let the rough grow thick in the week leading up to a tournament in order to make a tougher course, in addition to moving the tees back as far as they go.
Do you personally believe that there should be some sort of difficulty "bonus" added to tournament scores for handicapping purposes to account for this?
I personally don't because I see tournaments as the true measuring stick of one's capabilities (when that 4-footer means something is when you start to see people missing them), but I can see both sides of the argument since handicaps are mostly established through "easier" practice rounds. I see the main difference in the speed of the greens at a course, as some will go from having greens that roll 7 or 8 on a normal day to rolling a 10-12 on the morning of a tournament. This could affect the course rating (though I would imagine it would affect the slope quite a bit more since I don't have trouble with faster greens) and skew handicaps slightly if enough rounds were posted. At the same time though I feel plenty of tournament rounds will keep your handicap honest, the same way that other countries play competition rounds to set their handicaps.