Scala's Tail Recursion Optimization

In Scala, there's a lot of places where I think about, okay, this value on this particular call chain, it doesn't need to be computed. And so then I make it a lazy vowel. But that's something I have to think about is like, given given the execution structure of my application and different paths that I go down. Do I want this thing to be a lazy vowel or not? It's like, why am I making that decision?