In my experience, the number of words you write can be a reasonable proxy for the depth and intricacy of the argument. Granted, I also attend one of the best (if not the best) undergrad universities in the US, so this may only be true for a small subset of the college population.

Probably the most crucial factor in having a strong correlation between a high word count requirement and the depth of research needed to write that many words is having discerning grader who will penalize bullshit.

There are still some tricks you can play to make your paper look (slightly) longer--like not using contractions.