It's frustrating because consider how many hours are lost to compile times over the whole industry.
I have no idea how many people are slopping C++ code. So lets just calculate it per 1000. Assume modules save an average of 10 minutes a day.
1000 X 250 days/year X 0.167 hours/day -> 41,666 hours a year per thousand coders. Or 21 man years.
Yeah you'd think it'd be worth funding heavily.