[Geoff45 (Geoff)]

What do you want to use it for?--Surely one of the most irritating questions when you ask for something.

So I want some 3mm diameter ball bearings as part of a redesigned secondary mount for my Newt. Me: Do you have 3mm ball bearings? Bunnings Team Member (BTM): What's it for?
How is this going to help the BTM to know whether or not he has them in stock. Either he has 3mm ball bearings or he doesn't. It's irrelevant what I want them for.

Then I want a mercury vapour lamp to so I can see interference fringes when I test an optical flat. Me: Do you have a MVL? BTM:What do you want it for? Like he's going to follow the explanation.

I go into Sydney Glass to pick up some mirror blanks, which they told me over the phone was ready. See the guy on the shop floor and tell him I'm there to pick up an order for Smith. SG: What was the order?--Reasonable question, so I describe it---glass discs of such and such a diameter and thickness. SG: What's it for?
The list goes on and on.
Geoff