First of all they are not “licenses”. It is an AMA membership and a district membership.
All AMA events require you to be a member of the AMA so that’s the $39.00. Most district events require you to also belong to either their district or another one. Like in my area you have to have a district card (and AMA card of course) to ride but they don’t care what district it is as long as you have a district card.
Most districts have an award system. For example there was probably a District 14, 250A MX champion for the year. Most districts then recognize this person, and all other champions, at a banquet at the end of the racing season.