Think about it: with EMT, all it takes is one loose screw somewhere in the
line to sever, or at least seriously degrade, the ground connection.

So long as there is any kind of "connection" a fault will start an arc that
will "trip" the CB.

I was installing some foil insulation on a wall with a outlet box. The
foil just brushed against the hot wire and FLASH, POP the breaker tripped.
I guess the foil had been grounded by another outlet's plaster ears.