I think the idea behind that is basically that the license tests are a good way to isolate just working on examining one aspect of a car's handling, or one particular type of corner or group of corners. Taking it a step further, driving without any assists allows you to feel and observe the most directly the cars handling, so combining the two things is a natural idea for learning.
Turning off ABS reveals one of the tricky points of the game however, in that most cars tend to get loads of oversteer under braking with the default brake pressure settings. You cannot change that in the menus of the license tests, but if you assign the "RA" functions to your controller/wheel in the main options menus, you can adjust it once you enter the track. Restarting the event after doing so will make it remember your setting. Setting the rear brakes at least 2 or 3 clicks lower than the front is usually recommended, except for front-wheel drive cars. This all sounds a lot more complicated than it really is, believe me. You can use a second controller you're not using for driving to control the RA menu if you don't want to sacrifice any other buttons.
You might not want to just jump straight in to assist-free driving right away, but it is worth putting a little time into checking it out at some point. The game feels much different and more lively that way. It is also not necessary to do any of the license tests to progress in the game, they are just there for practice and completion and free reward cars. If I remember correctly, some or all of the license tests actually force some of the assists on, at least SRF. If there is any assist I would actually advise people to not use it's that one, as it changes the physics of the game in an odd way when your car begins to slide. This almost makes it seem like two games in one, and diminishes some of the value of the license tests if it is indeed forced on(I haven't run them in forever).
You don't need to do all the tests right away - this is a GAME after all

, but there is at least a little something to be learned from each of them. Just be patient, and use whatever settings(car/assist/options) feel right for you, but don't be afraid to tweak things as you go. You probably can't figure out everything the game has to offer in a couple days. The more you learn the more fun there is to be had.