I have to disagree.
Every airport in the system has some unique gate layout characteristic that makes a hard and fast rule inappropriate. What the norm is in CLT is completely different from DTW or SEA. If you regularly frequented all the different airports like the pilots do, you would have a better understanding of the minor issues involving crew ramp access.
Quick for instance, in LAS we are dropped by van from the hotel on the ramp at our assigned gate. What if the aircraft has not arrived yet? We are on the ramp, no escort, and no airplane, but there we are and we have not broken any rules.
There are a hundred and one reasons why I might be on the ramp without an airplane.