Because the C standard is notorious for saying things like the minimum size of an `int` is 16 bits. Changes in the size of data types would create issues when calling the Windows API or saving data to disk. Heck, the program is from the very early 1990's. C wasn't standardized until 1989 and compilers were notorious for having their own interpretation of C (what we would call extensions these days). Finally, developers often optimize large programs with machine dependent code. In the early 1990's, a full featured word processor would be considered a very large program.

Even today, C is not a terribly portable language when compared to it's modern peers. It is portable when compared to assembly languages and languages contemporary to its creation.

Hold on let them ask Claude again

it’s just because allot of projects throw in the towel

but some don’t

agentic engineering would make this easy, especially when following the blueprint of the projects that do this translation already