I didn't drop at all last year. Heck, I've made T32, but I'm not bragging about it here.
While I have nothing against the people who dropped to protect their ratings, I just find that stupid overall. Honestly, I don't really care for ratings because it would make me a completely different person.
I wouldn't drop at a Nationals at all, because it would be like, what's the point of going if you're going to drop in the end? Even if I have like nearly 1900 points, I'd still play all the way at Nats.
Keep in mind that there are people who drop on purpose because they want to screw with someone's resistance, so they would miss the cut.