How could you truly judge a driver's skill or a car's performance if they just show up 2 times and win. Maybe they drive really well in the rain, or maybe their car is only really fast at one track. I think you need the minimum competition rule to set the season winners apart from the race winners. Let the guy who shows up most brag about being champ, and let the guy with the best motor (or skills, setup, etc.) brag about winning races.

And just for the record, they should all come to the awards banquet for a beer.