A US federal court held that typeface designs cannot be copyrighted in Eltra Corp. v. Ringer in 1978. Federal regulations made this explicit in 37 CFR 202.1(e) in 1992. The government's explanation here [1] makes it explicit that typefaces are not subject to copyright protection, while fonts can be copyrighted as computer software.
[1] https://cdn.loc.gov/copyright/history/mls/ML-393.pdf