Not really? If I have a dinner party involving 6 guests, and my recipe calls for (<ingredients per portion>*6) then scaling down that ratio may give me 4.5 portions.

I don't cook things without purpose/specific goals. I'm cooking to make enough for the people I'm expecting.

That's not to say it doesn't make sense, just not how I've tended to see things cooked.

Around our house, we definitely cook with the expectation of having leftovers. While we do plan ahead some, a lot of our meals involve looking in the fridge and trying to figure out something to make with whatever raw ingredients happen to be in there, and hopefully scaling whatever spices/sauces/etc to match. It's only two of us, and we'll often cook 8-10 servings of something to have lunches for the next couple of days.

OK. What if you have a dinner party for 6 guests, but your recipe is written to give 8 portions?

What I'd do in this case (and this is true for most everyone I know) depends on what "portion" means:

- If it's something that can be reasonably divided among guests (such as a soup or something similar), then I eyeball the portions so they're all approximately even. Optionally, if there's an ample amount, you can simply let people decide how much they want through self-service.

- If it's something that's demarcated by physical objects (e.g. dinner rolls, cupcakes, etc), then you have a few other options: Leftovers to save for later, split them among people who want extra, or give them away to whomever wants them.

I don't know about the OP you're replying to, but I rarely divide a recipe up based on expected portions since portion size is highly variable. Should I have extra left over, then I deal with that accordingly. If I'm cooking to get rid of an ingredient, I don't particularly care if I miss the mark by a few portions provided I have enough in the first place for the objective.

(The other problem is that portioning in this question seems to me to assume that all guests are equally hungry.)

That's solving a different problem. Again: I understand how to scale a recipe (which is what you're describing).

Let's do this as a math problem.

How I tend to cook: Xbutter + Ysugar + ZFlour = 20 Cookies.

How OP is cooking: 2 butter + Ysugar +ZFlour = X

We're setting different known quantities (him butter, me portions) and then solving for the rest. They're fundamentally different approaches in cooking philosophy. And again, neither is "wrong" I just found OP's style to be novel enough to comment on