Why Do Most American Universities Offer Funded PhD Positions but Not Similar Opportunities for Master's Programs?

As a broad statement, I would say this question is false. This question is specific to program.

Some humanities and social science programs offer unfunded or partially funded PhDs. In contrast, many natural resource programs offer funded MS programs.

To expand upon the other answer, look and see if programs are "professional" or "research" programs. Some observations I have seen comparing the two types of programs:

• Professional master's degrees are sometimes Masters of Art degrees (MAs) and research programs are Masters of Science degrees (MSs).
• Professional programs often have more coursework and only a limited capstone project or thesis whereas as a research-based program will include a thesis that commonly produces journal articles.
• Professional programs tend to be tuition-based. Students are the revenue source. Research programs often occur in fields where MS projects get funded by grants (like the natural resource fields). Students do the work that completes the funding requirements.

Also, sometime service department with heavy teaching loads will use masters students to teach and provide TAs. Depending upon the size of the graduate program, these TAs may be open to professional masters students.

Why Do Most American Universities Offer Funded PhD Positions but Not Similar Opportunities for Master's Programs?

As a broad statement, I would say this question is false. This question is specific to programs.

Some humanities and social science programs offer unfunded or partially funded PhDs. In contrast, many natural resource programs offer funded MS programs.

To expand upon the other answer, look and see if programs are "professional" or "research" programs. Some observations I have seen comparing the two types of programs:

• Professional master's degrees are sometimes Masters of Art degrees (MAs), Masters of Engineering (MEng), or similar titles, and research programs are Masters of Science degrees (MSs).
• Professional programs often have more coursework and only a limited capstone project or thesis whereas as a research-based program will include a thesis that commonly produces journal articles.
• Professional programs tend to be tuition-based. Students are the revenue source. Research programs often occur in fields where MS projects get funded by grants (like the natural resource fields). Students do the work that completes the funding requirements.

Also, sometime service department with heavy teaching loads will use masters students to teach and provide TAs. Depending upon the size of the graduate program, these TAs may be open to professional masters students.