The difference between say mma drills and some forms is that mma technique comes about as a reflection of fighting. So the drill is supposed to look like what I would do if I was actually trying to apply the technique. Form work can go the other way in that people can try to apply the technique so that it looks like the form.
This last sentence is where my understanding of forms differs. Forms are not about a "look", but about learning the principles - how to move a given way while keeping balance, covering a certain angle, moving from one stance to the other, etc. With forms, the practitioner can learn to internalize these principles, then access those principles and basic movements when they are needed in application. The forms I'm familiar with (possibly not all, there are many forms I'm not acquainted with) don't create the art, they were created out of the art, based upon the techniques and movements used in combat. Practicing the form is just an additional way to work on those principles, another way of drilling. The exactness of the form, in my experience, gives the student something specific to work on when they are working solo. The variation within the form gives the advanced practitioner something to tinker with, when working solo, to explore some different weight shifts, slight alteration to stances, etc. to see what the effect on their own body would be. Then they take that information when they work with a partner, to see how that translates to an effect upon the partner. This latter part leads to new adjustments for open sparring.
It's not the only path to those adjustments, of course. I'm sure there's a parallel path somewhere in things like boxing, perhaps during shadow boxing or other drills, where solo discovery leads to adjustments in sparring.