The less effective a weapon is, the more time it takes to break through.
Axes and two-handed weapons are the most effective, followed by swords and maces, followed by spears, daggers and pike. It’s the pyrrhic act of a desperate general. The trade-off is that it comes at an extremely high price for the attackers.
This new last-resort feature has been made in response to community feedback, and is an important mechanic to enable the attacking side to still have a chance of besieging a settlement even when their siege engines have been destroyed.
Torching settlement gates has been replaced with the ability to hack them down with melee attacks.