plausible deniability. If your key can be brute forced and your intermediate CA is used by some bad actor, you can just say they brute forced it.
Versus: "The government ordered us to give them the keys and forced us to remain silent about it" - now all the damage lies on the government, who is likely known to already do stuff like that (or at least it isn't a surprise) and will hide behind the banner of safety or national security or something. (Whether it's true or not)