Their normal cores are so shitty that there is a reasonable chance that the wrong key will work to open the lock, especially if somebody is trying to open it quickly.

With LOTO locks, Bob could die if Alice's key works on Bob's lock. (e.g. both on working on equipment powered by different circuit breaks, and Alice confuses the breakers, and removes the lock from BOB's breaker, because her key happened to work on it).

A few reports of that happening, and their LOTO locks could be banned from many worksites due to unions rightfully insisting on it.

So it actually is worth having better cores to ensure only the correct keys will work.