What's the purpose of complex testing frameworks like this? What's wrong with using a simple framework whose tests must simply return a bool?

For example:

         var myObject = new Something("foo", "bar");	 
	
	 assert("simple operations", function() {
		return myObject.doSomething() == "baz";
	 });;
	 
	 assert("post-operational state", function() {
		return myObject.state() == 123;
	 });;
	 
	 assertAync("async polling", function() {
		return myObject.poll().length > 0;
	 });;

Note that those tests would be much prettier in CoffeeScript.

Is the purpose of heavy testing frameworks purely for the useful functions like "deepEquals"? If so, why not make a library with functions like "deepEquals" and use that library with a simple testing framework? Surely, there must be something I'm missing.

Edit: I should note that the beautifully written CoffeeScript compiler/translator doesn't use a testing framework (favoring a few simple hand-rolled functions), and it has a massive suite of tests.