I’ve genuinely never known a Mech Hanger to break and leave the Mech intact…
I have, several times. You may need to bend the cage back into something resembling a straight line as well.
Why would you not carry a few, light, potentially ride-saving spare bits? A set of brake pads, a chain quick link or two and a few links, a mech hanger, a couple of cleat bolts, a caliper-mount bolt and a few chain-ring bolts. I’ve used all the above at one time or another usually to fix someone else’s bike.
I’ve bailed out other people three times with missing chain-ring bolts before now, it does happen oddly enough.
But really, for the sake of carrying 50g or so extra in your pack, why would you not bother unless you really enjoy walking?