It’s quite simple. If you’re doing something niche (ie, it would be difficult to find similar examples online), and deals with highly critical code, it’s probably worthwhile to write it yourself, since there’s a high risk for it to produce bugs.

In my experience this was the case for writing a block driver & some other low level software.

It excels and arguably outperforms in some developers in other cases; app development, CRUD, and CS labs it finds on github. There’s still a risk for bugs, but an acceptable level considering the productivity enhancement IMO.