It is a major factor at actual tables, where players don't know what's coming and so manage their resources. CharOp boardwankery may see it differently.
That's because it's not in this thread.
What PF does is specifically define which natural attacks are primary and which are secondary. If you only attack with natural weapons, primaries never take penalties (no matter how many you have), while secondaries always take -5 (-2 with multiattack.)
So if I have a bite, 2 claws and a sting, in PF they are all primary and so I take no penalties, even if I don't have Multiattack. But if I have a gore and 4 hooves, the hooves are all secondary while the gore is primary.