What the title says. Assuming they actually did trust in the guard, I'm asking from a point of relative ignorance. I feel like this has been asked before, perhaps in some form in the recent past, sorry if that's the case.
More can be written, but you might like to start with "Considering how many Roman emperors have been assassinated by the Praetorian guard, wouldn't emperors be safer without it?" by /u/royalsanguinius .
This is not to discourage discussion. More questions, data, and debate are welcome.