WebAssembly is a compiler target, not a human-authored language. There is exactly one audience of people for writing wat by hand: spec and tutorial authors and readers. Anyone actually developing an application they want to use will use a compiler to produce WebAssembly. Prove me wrong and write Roller Coaster Tycoon in raw wasm if you want, but having written and maintained wasm specs and toolchains for nearly a decade, I will never write any wat outside of a spec or tutorial.
There is exactly one case where I'd like to write "raw wat" (and for that matter "raw wasm bytecode"): I'd love to do something like the "bootstrappable builds" project for wasm, starting with a simple wat-to-bytecode parser/translator written in raw bytecode, then some tools wirtten in raw wat for bootstrapping into other languages. :)