system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: In Formula 1, why aren't all the drivers given the same car to test who is the fastest?

Even if its only done as an exhibition race, that would be a far better way to determine the best driver given how different each team's cars are.
gpt
F1 runs two simultaneous championships: The World Driver's Championship, and the Constructor's Championship. The driver's race is obvious - he with the most points wins. The Constructor's championship is awarded to the *team* with the most successful car. 

Each team builds a car, and runs two of those cars with two different drivers. This means each team has to design the best car they can within the rules, and each team pushes the rules as best they can. Whether or not this makes for good racing is a matter of opinion, but the idea is to get teams to innovate as much as they can. 

This is how you get things like the Mercedes turbo units, which are moved away from the engine and pull much cooler air, generating more horsepower and less heat. It also means you tend to get staggered finishes by manufacturer... 

NASCAR, on the other hand, races almost the same car. They're manufactured by different companies, but they're all building to a stock spec. If you're looking for road racing, rather than ovals, you might look at F1's feeder series, GP2. GP2 teams all race the same engine, chassis and tires, so it's a much better measure of driver quality.