Because of how weak the boy groups are on the charts. Someone's horrible take in that recent aespa thread inspired this one.
Think about it.
Who are the groups that have been getting all the PAKs in Korea for the past 5-6 years?
All girl groups.
Who are the top K-Pop groups of this era?
All girl groups and it's not even debatable.
But think of the previous generations.
The girl groups were battling (not literally obviously) for supremacy but the boy groups were JUST as competitive.
Big Bang? You kidding me? Chart monsters
BTS? Duh
EXO? Used to ruin the charts for everyone
Wanna One? Digital monsters for as long as they existed
iKon? Had one of the biggest hits of the 3rd gen and ate up the charts pre-scandal
Winner? Had several big HITS like Really Really
And don't get me started on first gen
tl;dr Girl groups are still hard carrying and remain each other's biggest competition on the charts...other than Big Bang currently, which kind of proves my point.
We might not see a boy group get a PAK until 2030 at this rate.