The following note disclosure appeared in a recent annual report of Halliburton:

Our receivables are generally not collateralized. Included in notes and accounts receivable are notes with varying interest rates totaling $$12$ million at December $31.$ At December $31,39\%$ of our consolidated receivables related to our United States government contracts, primarily for projects in the Middle East.

Explain the reason that Halliburton indicates that its receivables are generally not collateralized. What significance does this have to the reader?