Over 100yrs ago, a war between Alternating Current (AC) and Direct Current (DC) development was waged between none other than Nikola Tesla and Thomas Edison. Tesla believed that due to excessive losses, DC was inappropriate for the long distance transmission of power, while Thomas Edison believed that AC was dangerous. Fact is, Tesla was right! DC does exhibit significant voltage drop over a distance... even as short as a few feet. The longer the cabling, the more voltage drop occurs. This can be a real problem, resulting in poor or loss of operational performance of the device being powered.
This is a significant concern for the RV owner as one must always be mindful of what the ramifications are when adding loads to an existing circuit, or when sizing wiring for a new circuit. See my tutorial High Power DC Wiring for an in-depth discussion of this phenomenon. Typically you will run into difficulty from voltage drop issues long before you will exceed the current-carrying capacity of the wire.