My 2 cents
The guys that do string alignments all the time, its more accurate due to the level of repetition required - they achieve accuracy and consistency through practice. Also, the race guys don't always have access to a big machine, when you're "out in the field" its likely your alignment rack is back home.
I'm maybe going to do one or two alignments per year but I hate going to the alignment shop. Because I don't do string alignments all the time I had trouble finding good consistency. Decided my compromise was hubstands, lasers, and scales. I paid more money to make consistency easier.
"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."