In NSW a learner drivers speed limit is 80kph. A P1 driver is 90kph. I'm pretty sure they set those limits for the safety of the occupants & other road users while these people learn how to drive & be in control of a car.

Why is it not ok for someone who doesn't feel comfortable to go a little slower? Better than them going faster than they can handle & loosing control I would think?

I do understand, & I also get frustrated, but I'm not going to push anyone to go faster than where they feel safe...
While they're learning, yes absoloutley.

But if an experienced driver can't drive at the limit without losing control, they quite obviously are a danger to other road users and should not be driving.