Pinans katas etc are good teaching vehicles to exercise a large group while doing martial arts moves rather than simply exercise. It is helpful for moving a large group as well since you don't want everyone crashing into each other - and you can address adjustments as they stand out easily.
However kata has its place and it is a piece of the picture and should take a back seat to actual interaction with physical application/bunkai of technique. It helps students take home homework since they can recreate the moves on their own if they have been drilled with it. Again, not a replacement to actual interaction as many watered down schools have made it. If you watch a heavy emphasis Kata student vs one where interaction is emphasized, the kata focused student is very choppy and often can't hold their own. Watch the performance of some past advanced black belts from schools where they were kata champions that have entered UFC or kumite - they get clobbered quickly.