I say this because it would be nonsense to even play flam exercises (within a drumline) if you don't even have a single flam in the show.
So when the senior who writes warm ups for a line with no instructor graduates, and those kids have a show the next year chock full o' flammy goodness, and nobody practiced their flams for a whole year (impossible, in my opinion) nor do they have warm ups to practice flams, how well do you think they'll do?
It is always good to practice every single rudiment, regardless of whether it shows up in a halftime/winter show or not. It's just a general preparedness thing.