The average investor confuses a US Royal Trust (USRT) with a MLP; it is comparing apples and oranges. The only value of an USRT is the commodity up for sales, or more exactly what is left to sale.
The MLP encompasses the commodity plus some of the infrastructure or even another corporate entity. This is why an MLP has “Earnings before interest Taxes Depress Amortization” (EBITDA). It is possible for the profits to be less than the taxes and amortization combine.
USRT once IPOed cannot be changed or modified. MLP can be modified in many ways, this is why MLP earning may be based on a different model, such that a pipeline can be added or sold for example. An USRT can be formed for any reason, but a MLP model must include some kind of commodity. This is why O&G MLP are attractive, especially to raise capital rather than asking a bank for a loan. USRT has the same function, raise capital, but without any flexibility. This capital, more time than not, is to repay a loan, USRT must have a distribution to be IPOed, within the stated distribution intervals.