Another positive feature of Laura's short answer is the writing itself. The repetition of sentence structure ("I don't ride.." in the first paragraph and "I ride..." in the second), creates a rhythmic feel to the essay much like the riding of a horse itself.
Next, you should know how to train an unbroken horse.
What clearly comes across in Laura's short essay is her love of horseback riding.
Laura isn't someone who rides horses in an effort to build up her extracurricular activity resume. Her passion for her favorite activity is unquestionable.
On the flip side, a short answer on starting your own business can weaken your application if the focus and tone are off.
How you write your short answer is in many ways more important than what you write about.