I could certainly imagine that if e.g. Waze warned about railroad crossings that it could prevent some small percentage of almost sleeping drivers/truckers getting hit.

It's a numbers game. 999/1000 will be watching just fine without a warning from their navigation app; that warning might bring awareness to 999.8/1000 or so. Or something like that. That could result in a pretty dramatic decrease of accidents.

This seems like a no-brainer to me - they should add a (visual) warning about this.