I decided to because it would give me a reason to work on technique (with the scales and arpeggios and such)
I was wondering that myself when I was deciding whether or not to take the exam, but I decided to because it would give me a reason to work on technique (with the scales and arpeggios and such) and because I actually liked the pieces on the syllabus, so it wouldn't be a waste of time. Also, I plan to include a music supplement with my college application, and I think an exam result would strengthen it.
doing the exams may be a good way to add structure into your studies of classical piano