Liberal arts includes STEM majors. For example, biology, chemistry, and physics are all classic liberal arts majors that exist in any standard definition of “liberal arts” and are typically offered at LACs. Math and CS are also sometimes considered liberal arts as well, which can depend on how the major is structured.
If you mean a non-specialty college that only offers non-STEM majors, I agree that there aren’t many which I expect largely relates to tradition (LACs traditionally offer liberal arts majors, which includes some STEM majors), lack of demand, and challenging to sustain financially. However, there are some exceptions beyond the specialty schools that have been previously listed. For example, Thomas More College of the Liberal Arts only offers one major – Liberal Arts.