Why would one use a POST-based search engine on their website?

I'm aware of the differences between GET and POST (security and caching, in particular). Additionally, when I search this question using Google, I'm only greeted by results telling me how to hack site search in Google Analytics for POST-based engines. I already know how to do that.

What I'm wondering is why employ a POST-based search engine in the first place? What are the salient advantages? I can't imagine why site search queries would need to be secure. So maybe it has something to do with caching?

Thanks so much in advance to anyone who can shed light on this.