Record ID number and concatenate function

The ID number assigned to each record is the bane of my existence.  I have a table that shows the events (stages) however the stages (which are numbered) were not entered sequentially.  This table is linked to another, and the column that where I want to show the stages completed on that particular day show up out of order.  The concatenate function for that column applies to the ID number and not the value of that particular field.  All other functions (AVG, SUM, FIRST, MAX, etc) apply to the actual field value (stage number) instead of the ID number.  Why is this?  I know that the ID number is unique and cannot be changed, but why does the concatenate function not apply to the field value like the rest?