Consciousness a byproduct of brain functions? Or even so a waste product?

I read in Jonathan CW Edwards, 'Is Consciousness Only a Property of Individual Cells?' paper

"However, as Seager (1995) has pointed out, a brain has many different functions at different structural levels and it is not clear why one or other should be endowed with consciousness."

What it struck me here, is the phrase 'endowed with consciousness'. Brain functions endowed with consciousness and brain functions that don't? Referring to consciousness as an attribute or property that a function, a brain function at least, could have or not? Is it not consciousness a function in itself? What is a function? A dynamically evolved association between objects or states. Or as it is described here

"The mathematical concept of a function expresses dependence between two quantities, one of which is given (the independent variable, argument of the function, or its "input") and the other produced (the dependent variable, value of the function, or "output"). A function associates a single output to each input element drawn from a fixed set, such as the real numbers."

Its mathematical definition, the groundwork of function, a dependence relationship between what it is 'input' with and what represents the result, its output. A function, brain function again, that while it is underway, it produces, beyond its expected output, (since it is endowed with consciousness, a sort of privilege) consciousness as well. It is not the brain function's primary goal, what spawn it or responsible for, in the first place but nevertheless, consciousness comes out too. So what is consciousness then? A byproduct of some brain functions? Or even, as in several cases, a waste product?

Is it not consciousness, a function in itself then? With its own input, as well as output, in a dependence relationship between some objects or quantities involved? This line of thought approaches some other thoughts I expressed before, consciousness looked, as even as, an extra baggage carried along, piggy-backed by more crucial brain functions that goes along, as far as I can tell, with epiphenomenalism, mere mention sufficing, focusing on the substance of the problem and not the procedure.

May this be how consciousness arises but the crucial issue is, its usage. How do we use that gift given to us.