Years back I worked at a C++ shop with a big codebase (hundreds of millions of LOC when you included vendored dependencies). Compile times there were sometimes dominated by parsing speed! Now, I don't remember the exact breakdown of lexing vs parsing, but I did look at it under a profiler.

It's very easy in C++ projects to structure your code such that you inadvertently cause hundreds of megabytes of sources to be parsed by each single #include. In such a case, lexing and parsing costs can dominate build times. Precompiled headers help, but not enough...