Sows with cubs also stay in the den longer. Nature makes sure the boars and barren sows leave the dens first and begin to feed. That way when the sows bring the cubs out it is safer for the cubs. Bear can be cannibals when they are really hungry and it isn't unknown or even unusual for boars to target cubs. If they have been actively feeding a couple weeks they are less likely to kill and eat a cub.

This is why they schedule the spring hunts when they do. The season is over by the time the cubs come out. It is very rare to see the cubs during the season. I used to hunt CO's spring season a lot before the bunny huggers shut it down and I don't think I saw more then 3 or 4 cubs in all the time I hunted the spring. Of course, it was the very slight possibility of orphaned cubs that the bunny huggers used to stop the season. We had a lot fewer bear problems back then too.