What's the purpose of the Spear?

Thought I'd clear the personal order real quick.... Sweet liberty, what is this item even for? - has to lock on to be used - only locks on to certain enemies - mid splash damage - only 4 shots - has to be reloaded between shots - no movement during reload - reload requires a backpack - 8 minute cool down.

I've only been playing a few weeks so it's possible I'm missing something.... but it seems genuinely awful. It's seemingly outclassed by multiple items on every front. So, genuine question: what role does this support weapon fill better than anything else??

Edit: I appreciate everyone's answers here! I have new found appreciation for the spear ... Though it's probably gonna still be pretty low for me personally, I can see it's value.