Why do you need prototype testing?

Question

Why not just make the darn thing.

Answer 1

A prototype is a playground, if you will. You can test things out, throw them away if they don't work out; iteratively find out how things might work with real users, etc.

Prototypes test specific aspects that are unclear or not yet fully determined and as such are easier to implement on their own than trying to figure out how to integrate something you don't quite know yet into a complete system. This also means that it doesn't hurt too much when throwing them away.

It's not uncommon to implement prototypes without any actual programming. Paper prototypes and interactive PowerPoint slides are examples of that.

Answer 2

So you don't get fired when it doesn't work.