When the map is the same. Because waiting 30 secs or more every time I want to change vehicle or circuit sucks.
For time trials, I usually want to try distinct cars on the same track. Having to reload everything just to change the car seems unecessary since nothing really changes for the track. If you unmark the "Competitive Scenario" option you can change the car without reloading but the time is attributted to the original car that you started the time trial with. Inconvenient if you want ot keep track.
