probably the same as why our men do so badly internationally given the quality we have abroad. Low game time, and actually playing/training together.
I reckon its lack of depth/quality more than anything. There are one or two playing at the highest level, but not the same as their opposition, take the Olympics for example Sweden, USA and Australia have more players at higher levels.
Players of their quality are dime a dozen in Europe (men even more so), just you wouldn’t recognise someone playing in Iceland (Hassett) or a US University (Cleverly, Rennie) if they weren’t from NZ. Same as how you wouldn’t know Lillestrom’s (team above Joe Bell’s Viking) centre mid, or wingers for Fredericia (equal points as Helsingor) or a kid in Torino’s u19s if it wasn’t Matt Garbett. It’s why I don’t buy the expectations people had for the teams in Tokyo, both teams were odds on favourites to lose in all 7 games, the women were just more unlucky than the men
Though think OlyWhites on paper were probable favourites to win the game they lost, being Honduras. That's after the Honduras senior team were playing in the CONCACAF Gold Cup at the same time as the Olympics with some of that country's best U23 talent, and the 5-0 thrashing dished out by our U20s in the 2019 WC. Woud/Stanger sadly had a mare, and Hay acknowleged he got it wrong by not making more changes to the team following a big effort in the sapping heat against Sth Korea in game 1.
But your overall point that there are many many other countries, with as much or more young talent (mens & womens) playing in Europe as us, stands for sure. No doubt the playing stocks of NZ's mens football are rising, but that's likely the same for many other 'developing' football countries, as they build their own new shiny academies, FIFA throws some cash around etc etc etc.