There are two different ways to handle spacing and fonts:

Proportional (modern) typefaces have very carefully designed spaces that are optimized to be used only once. Most modern text editing programs will even remove a second space. Even HTML will ignore extra spaces unless explicitly coded.

While using two spaces is great for monospaced fonts. These are usually found in Typewriters, 80's era software, and Coding/Terminal programs.

But above all, it is ultimately about what looks best.