The idea is that a simulator controls the number of decisions per minute
that you, the pilot, have to make. This allows effective learning. In
a real airplane just about anything can start happening at anytime,
complicating the learning.

exactly. Especially with ATC calling out traffic or an approach is
down for MX or the winds don't agree with the VOR approach you want
to do.

The other thing to keep in mind is when you fly IFR, you fly IFR.
You don't 'practice IFR.' Ok, you can do VFR practice approaches
but you still have to do them as ATC expects you to do them the
published way. The first time I went up with my CFII out of SQL,
our clearance was 'maintain VFR at 1100 or below.' I didn't have
the skills to do that, checklists, call departure, etc. and I busted
altitude by no less than 50 feet. ATC was on my ass immediately.
You 'do' and not 'practice' in the system. The simulator helps
that.

Gerald