Granted in real life you won't have a spotter on a road coarse, but in real life you'll have much better awareness of what is around you than in an artificial environment like this.
IRL, you can swivel your neck or glance at side mirrors while your peripheral vision keeps an eye on the road, and your peripheral vision can spot other cars next to you.
In LFS you can use the look left and look right function, but compared to all the sensory info you'd get IRL, it's a crude approximation.
I use pit spotter to overcome some of the gap between real life and simulation.
I tend to have a few less incidents because of it and I think that's a good thing.
Besides, I have no natural talent, so I need all the help I can get. :P
FYI, I do still check mirrors and look left and look right even though I use the spotter.