why dont humans make houses from whatever mud wasps use?..

They did, the Inca's stuff is all there and even Pompeii which got blasted by a Volcano

Go to the outback and do it.

They do: adobe houses

Btw I read all the nancy drew and hardy boys books i could find when i was a kid

Adobe is probably number one building material for home in the world. Especially 3rd world countries.

We don't make the right kind of spit. 😆

We do use "mud".

Only, we mould it into blocks, fire them and call 'em "Bricks"...