It can be worse than that, one build system I looked at built everything every time. Why? Because "Computers are fast enough that trying to figure out exactly what needs to be rebuilt is an anachronism, this can rebuild everything in the time it took that crufty old system to figure out what it actually had to build."

I've given up trying to educate folks, I just make a note to check in with them, 6 months to a year later, to see if they are still building everything.