Answer:
Some will use me, others not. Some have remembered, others forgot. For profit or gain, I'm used expertly. I can't be picked off the ground or tossed into the sea. What am I?
In buckles or lace I help set the pace. The farther you go the thinner I grow.
Of the king I am blue and of the peasant I am red. Of the frog I am cold and of the dog I am hot instead.
Use me to reward good behavior.
the only amusing part of the body
No matter how little or how much you use me, you change me every month.