F# Lazy Evaluation vs Non-Lazy

I'm just beginning F# so please be kind if this is basic.

I've read that a function marked lazy is evaluated only once and then cached. For example:

let lazyFunc = lazy (1 + 1)
let theValue = Lazy.force lazyFunc

Compared to this version which would actually run each time it's called:

let eagerFunc = (1 + 1)
let theValue = eagerFunc

Based on that, should all functions be made lazy? When would you not want to? This is coming from material in the book "Beginning F#".