This. Plus you can’t repopulate an entire laying hen farm at once. The large million plus hen farms are brought back into production in stages.I think most meat chickens are killed at 6 weeks old or so, whereas it takes a lot longer to grow an egg producing chicken. So the rebound if you exterminate a flock (which seems like the wrong way to do it but not my decision) is quicker with a 6 week harvest than however long it takes egg producers to mature.