Documenting and tracking the impact of minor adjustments made to a cars setup: camber, caster and toe angle, tire type and pressure, fuel load, spring rates, suspension compression and dampening, brake bias, ride height, etc. is critical to achieving maximum performance for the car and driver on any given race day. There's an awful lot to consider here, weather and track surface condition also play a big role.
With the ability to capture the car's telemetry generated in Assetto Corsa, iRacing and rFactor2 using tools like McLaren's Atlas or MoTeC's i2 Pro, a serious sim racer can now easily document and track the impact of changes to any car's setup at a specific track in specific weather conditions. It's also easy to compare your performance as compared to another racer if the telemetry log files are shared.
Another great reason to invest in the best racing simulator that you can afford from a company that understands the importance of data analysis and providing a best in class experience.