to prevent abuse / misuse also its only a trial phase which needs training via mods/admins. Would be convenient to have the powers but it's just a training/trial phase
To prevent abuse. Also so they don't go silly and slaying with permission. That's the reason they can't staff with an admin.
Trials don’t have any power because well, they are in a trial phase. When a trial is first promoted they are almost always slow or semi-inaccurate (which is understandable and completely expected), and giving them powers would create a possibility for someone who doesn’t know what they are fully doing to make bad decisions. Trials are there to train so they can become a full-blown staff member, so giving trials premature powers is just not a good idea.
Because it is a trial period to see if someones attitude, decision making, and general behavior for full staff. During trial phase they answer reports, and tell the mod/admin in game chaperoning them the result. When in game alone, they are just normal players.