First, I know more than well how it feels to be doing a major contribution to a zone while others are just sitting at a line. Heck, yesterday had a skill zone where I put down 1.1m points to the bar on my own even though we had five people showing for the forzathon.
People want competitiveness, and others do not. All of the non PVP co-op play is set up without any sort of bias towards any other member of the team.
Maybe it has to do with seeing the best in people vs seeing the worst. Me? I tend to always look at how people will abuse said systems and negatively impact others. By having a reward advantage, it has a balance of what positivity does it give to the event vs the negatives?
Now if you are an optimist? Well it benefits everybody. All people will compete to get the job done and to get it done faster! Fun and good times!
However, I view it differently. The only person who will cheer is that one who got the reward. The others all going to be most contributive? Well you have just made a casual non competitive group experience a competitive one. So now people who do not want to do competitive play stop coming because they missed out. So as soon as you have more than one person in that group who is actually wanting that most contribution award, you have now negated any positive moodlet that can come out of it.
It wont incentive the people who just sit around and stare or bring a D100 car. I mean… they brought a D100 and are turning in circles honking a horn or AFK, clearly they do not care about the results. They are probably AFK or watching something and just want the free handout while they eat dinner or something. It would have to be one heck of a bonus to get them to actually aim for it. But now we have a bigger bonus, and that means any negative moodlet is even worse.
That was just for the highest contribution bonus.
Now lets not have that. Lets make it a leader board. The only place this could benefit is the skill zone… but then it also is just the biggest contribution. If it is the single highest skill bonus, then you will have players taking more risk to get that ultimate and not add anything until the board is almost filled or they have enough to fill it from its current location. They will metagame to ensure they have the maximum bonus possible. Now we have what… 3? 4? More people all aiming for biggest score, but only one will get the drop into the scoreboard. Everybody else contributed nothing in the end.
Every other zone though, drift, speed, jump and all them? Once you toss in a reward for a max bonus, it will make the event take longer. A maximum top speed runs into the speed traps is wasted time for the event. There comes a point in which time spent for the acceleration and deceleration for a differential in speed is more than the time taken to stop and turn around. If you are pulling in your highest gear at a speed trap, jump etc then you are reducing your own contribution. Drift zones are similar. There comes a point where drifting in an area for an extra bit of points on the single run reduces your points per minutes overall.
It is the nature of a competitive attitude. Competition causes adrenaline and aggression. It means higher high when you win and a lower low when you lose. The results of these changes is pretty much dependent on how you view a gaming community and other people. Though I am pretty confident it will end up like above if they added the individual bonus points. It will make harder and take longer on the competitive people, and the more competitive, the faster they will get frustrated and the more negative the moodlet instead of the semi casual experience it is.
Edit: But along lines of your idea, perhaps a bonus based on time completed and number of persons present? Combine in a mechanic to verify regular active play vs score once and afk. Keep the reward global for the group, but perks to the extra success overall.