Probably because she is one of the few units that is insanely easy to CR, just slap two copies onto her and usually the second one can get her to that golden dream.
But yeah, CRing her isn't that much of a big deal enough that it needs the next best thing to a religion on the subject. The only reason why it'd be necessary is if you're dealing with a map where the unit point pool is strained to the point where every unit placed matters *coughDangerintheOasiscough*. But that is never really a problem since UP generators like Katie and the whole band of soldier units with Call Reinforcements exist, and they're usually the first units placed.
Not to mention if some people got lucky with premium rolls at the start and got units up in the black/plat rarity that are decent or supremely efficient for their cost, they usually carry maps at the start and usually let you get away with placing units with high costs.