While one may not be interested in writing compilers, the techniques are applicable elsewhere.

For example, I once wrote a date/time "compiler" that could read dates and times in various human formats and construct a time_t from it. It's a giant mess if you approach it in an ad-hoc fashion. But if you approach it from a lexing then parsing standpoint, things work a lot better.

I see too many attempts at reading a textual data format that are done ad-hoc. Even worse are the attempts to design a data format where the designer clearly had no awareness of lexing and parsing - the format is just one ad-hoc kludge after another.