It's easier to end up with underexposed/underdeveloped.

In northern climates, things cool off quickly and developer weaker.
It's easy to forget or get distracted in agitation cycles.
It's easier to underexpose as a choice rather than get motion blur
You get more grades/flexibility if needed when printing by underexposing.
scanning tends to work better with underexposed rather than bulletproofed overexposed.