Here is the thing. Players that are 13-16 are like minor league players in baseball but not real investment needed. They are free to get(minimum salary and no need for a draft pick) and can sit on the bench for a few years. If they pan out, great, if not, you just grab some new players. Every NWSL team should have at least two. You look for impact players in FA, good players in the draft, and long shot prospects in the underage group.
It should be noted that the past 4 weeks has been a chance for NWSL teams to play their complete teams since the games meant nothing towards standings. With 56 players at the Olympics this has been a chance to see what you have, and get some experience for the younger players.