Why use Pierce with exploding projectiles?

Good day all. Help me understand who so many players use pierce. As I understand it, any projectile that can explode for AOE damage, only does so when the projectile impacts something or reaches the end of it's life. If a projectile pierces a mob, it won't explode, rather it will continue on until it impacts something else, or expires (end of life) ... in which case the boss you are attacking and who is trying to claw your eyeballs out, may or may not take AOE damage (and I'm still not clear whether the pierced mob even takes physical damage). If you have a high chance to pierce, this could occur quite often during your boss fight. Any help would be much appreciated.

Happy Hunting

Pierce is mostly used with Ice and Tornado shot as well as Split and Lightning arrow.

It's good for Split and Tornado because they already multiple projectiles and it's more popular there than chain because of no damage penalty so you don't have to swap it out on bosses.

Lightning arrow and Ice shot are exceptions to the 'no special effect on chain/pierce/fork' rule so pierce is also popular there because of shotgunning-like effect you get when a lot of enemies are bunched together.

It isn't very popular with spells because most of the projectiles you would need to pierce with already do so.

Because Drillneck.

that only occurs with explosive arrow. for instance, vaal burning arrow will explode in an AoE but does so on each mob it hits even while piercing through them. so instead of just one big boom you'll get multiple with pierce.