Cymbals, moreso than any other section, have the unique ability to be part of the musical and visual package at the same time. They provide both the crash and the flash. Sadly they're a bit of a dying breed; some bands are content to put all crashes in the pit and not march even pits, an issue seen even more boldly in drum corps. Still, those who still hold it down in many bands take true pride in their craft.
Excellence at cymbal playing demands 100%. After all, a wrong note in the flute section can be covered up, and even muddy diddles in the snare line can be missed. But there's no hiding an errant cymbal crash.
True enough, there are many cymbalists who are "also-ran" percussionists or even double-reed players who can't march their instrument. But if you get a line who truly gets it and loves their plates, well, it's one of the finest things marching music has to offer.