This is useful in a plain-text based document system, for producing nicer rendered output. Box diagrams typed up in a man page can be rendered more nicely in a HTML version.
It could also serve as part of the markup input language in a system like asciidoc. The benefit is that the source resembles the output.
For displaying "inline glyphs" made of sequence of consecutive characters there is option to use font with corresponding ligatures baked in, such as Fira Code [0].
Yikes, LICENSE! Full of how it may or may not be sold phrases requiring a lawyer to understand to answer the question, "can I stick this font into a PDF that could end up in some software distro that could end up being for sale". The LICENSE appears to involve users into a contract; i.e. is not a pure license grant. 2-Clause BSD or fsck it.
In a HTML rendering, references to exotic fonts are pretty much a nonstarter, unless you include them in the page.
Actually I use a tool similar to this (ditaa) to generate drawings in an automatically generated reference manual frop ascii code diagrams in source code. There's definitely a good use for it.
