its definately more common in the last 1-2 years to see people racing from a roll.. i am sure that this is because of the additional police presence during popular "meet" nights. a few years ago and earlier, we used to be able to go to a street, "track" (it would be a rural street, sometimes in industrial business areas, with no other civilians around) and the amount of cars would range from just a few to 25+. we would be able to stay their and run cars from 11pm to 2-3 am with no police presence. if the police did come, they would ask if everything was safe, "yessir" and the cops would be on their way. i would pretty much always watch and never run, but for the most part, it was kept mature, responsible and safe. nowadays, with the same conditions, the cops come out and break things up 5 mins in, sirens and everything, ticketing etc...
great advantage of going from a roll is its much more mobile and harder for police to predict what stretch of freeway you are on, especially if their are several freeways to choose from..
alot of ricers etc, will also complain and cry about getting a bad launch, missing gears and wanting to run again, which is very much minimized in a roll race. (what they should really practice is getting used to the fact that they cant launch worth **** no matter how well they launch)
but overall i believe, u make a race car to be best at as many things as possible, dig, roll, autox, road course etc.. versatility is key.