The language of science is mathematics, so code that more closely resembles mathematical notation can be more efficient for practicing scientists to understand. There's a lot of value in code that looks like the expression published in the paper, because when another scientist wants to build upon or modify that code, they'll read and understand the paper first, not the package code.

Also in physics, sometimes you get really large expressions with a lot of Greek letters and operators. In the paper, you make it a double-wide multiline equation with LaTeX. It makes a big difference if that corresponds to a few lines of Greek symbols in your code, and not twenty.