Do I need an iPad if I have an iPhone?

I'm curious, do I really need an iPad if I already have an iPhone? I understand that they both run on Apple's iOS system and have similar capabilities, but is there something unique about the iPad that makes it a necessary addition to my tech arsenal? I'm trying to be mindful of my spending and don't want to invest in something that's just going to be redundant. So, what are the benefits of having an iPad that an iPhone can't replicate? Is it worth the extra cost?