about theorycrafter : FFXIV doesnt show your %chance of getting a critic. You dont know how much you have with 0 in crit score, or with 2000 in. so... before doing mathematics (because bards get proc due to critical if it didnt change with SB), they have to being able to calculate how much critical for 1%... => spamming skills and parse this to have an idea. then repeat with another, and another, AND another crit score, to define (not perfectly but close to it) the crit score => X% crit.

Before SB, we had miss chance depending again on a secundary stat. accuracy. Too much acc => lost stat. not enough => chance to miss. So, knwing the hard cap (THE exact score of accuracy to have 0 miss chance) was mandatory to optimize stuff. How? doing the fights, and then, reading how much miss, then there was some people collecting all data from numerous players, to have the exact score.

And yes, no more accuracy, but... we need it for critical... it changes each expansion.
So, before saying a parser is useless, try to do all those guides without.