A cell formula defines a computation, but not a function. For it to be a function you have to be able to reuse it (call it as a function) in multiple places.
For example, you can't define the abstraction "square" in Excel. You can compute 2 * 2, A1 * A1 and so on. But there's no way to define a construct which given x produces x * x, then reuse that construct everywhere you want to square things. Everywhere you want to square something, you must inline the computation. That's the absence of functional abstraction.
For example, you can't define the abstraction "square" in Excel. You can compute 2 * 2, A1 * A1 and so on. But there's no way to define a construct which given x produces x * x, then reuse that construct everywhere you want to square things. Everywhere you want to square something, you must inline the computation. That's the absence of functional abstraction.