Is it at all possible that different people like different things, or maybe think differently, or perhaps find different workflows to be productive? If you could buy any of those as anything less than totally preposterous, then you may be able to make the next jump to considering why people like a development practice that differs from the one your prefer.

I like tests as more of a 'checkpoint' thing, myself. To each their own. Also, I spend most of my time in a REPL, which I suppose is pretty close to what people tend to get from a TDD kind of loop.