A reset is intended to set all clocked circuits in a known state.
On one of my designs a reset reset a "2 NOR gate latch"

But some circuits can also suffer latchup issues, in which case you can play any number of times with the reset without solving the issue. And it doesn't even need to be on a port pin - with enough abuse, where you just can't keep gnd and vcc locked down, even inside logic in the processor or external chips can suffer. In some situations, you put a charge where a charge shouldn't be, potentially requiring a power loss for hours because you got something similar to a memory cell. In other situations, you just create yourself a thyristor - it's enough with a short power removal to unlatch the signal.
I guess some of the above are unavoidable, but those I have been exposed to, when involved with the product, I have removed with design changes. (In one case as simple as grounding an unused pin)

I am 200 miles away from my magazines, so do not ask which one, but in one of them it is mentioned that someone had to power cycle his kitchen exhaust fan, if you can't even get something that simple to work w/o glitches, THAT is the ultimate argument for including the watchdog.

Erik