mulegolf, why shouldn't it be two strokes? For OB, for example, the idea is that you hit the ball off the course. You take a one-stroke penalty for that. Then, you hit from where you were BEFORE you hit the ball off the course. (That's the "distance" part.)
So if you just drop and take a one-stroke penalty, you've essentially advanced the ball 230 yards (or whatever) without a stroke. In essence, just picked the ball up and moved it 230 yards. Hardly seems fair.
My advice is to always hit a provisional when you think the ball might be OB. But if you don't do this, and you don't want to go back to the tee (which I understand), then you at the very least need to assess yourself a TWO-STROKE penalty, not a one-stroke penalty.