Ahh, the scale thing.
It is immediate feedback on the day. I know that if I weigh 260 lbs at night that I will weigh 258 in the morning. Pretty simple, I know that I metabolize and dehydrate 2 lbs overnight. However, if I weigh 258 in the morning, but 259 at night, I will probably be 257 in the next morning.
That is why twice a day. I also know, if I go up 3 lbs during the day, I need to look at my log and figure out why.