Then why do most have a "defeat mechanism" that only takes a screwdriver to open it with the switch closed? Just curious. I'll bet even unqualified folks can use a screwdriver.
The accepted issue there is that one must have a tool in their hand, which makes it a WILLFUL effort to open the enclosure with the power still on. You can't accidentally open it in trying to steady yourself, or casually open it just out of curiosity while walking by.
The NEC is a little loosey-goosey on this, but there are generalized requirements for preventing casual access. Check out 110.34.C, 430.232. Not exactly condemning the omission of door interlocking, but it does imply that it must be safely done.
But NFPA 79 however is very clear.
5.3.1.4 Supply circuit disconnecting means mounted within
or adjacent to the control enclosure shall be interlocked with
the control enclosure in accordance with 6.2.3.
6.2.3.1 Each disconnecting means mounted within or adjacent
to a control enclosure that contains live parts operating at
50 volts ac (rms value) or 60 volts dc or more shall be mechanically
or electrically interlocked, or both, with the control enclosure
doors so that none of the doors can be opened unless
the power is disconnected. Interlocking shall be reactivated
automatically when all the doors are closed.
NFPA79 is the Electrical Safety Standard for Industrial Machinery. So if your equipment is not considered "industrial machinery", they may be able to make an argument for their omission. However, any AHJ could decide otherwise and you might be left holding the bag.
automatically when all the doors are closed.