Why the low rates?

Fed: The velocity of money is the frequency at which one unit of currency is used to purchase domestically- produced goods and services within a given time period. In other words, it is the number of times one dollar is spent to buy goods and services per unit of time. If the velocity of money is increasing, then more transactions are occurring between individuals in an economy.

Velocity is your sample transaction rate, it will be related to the yield curve.  Think of the yield curve as the probability distribution of a finite set of sample rates.   Sample rates are down, the curve is flat.