Sure, but we can't call them PowerPoint presentations either.

How about "Presentation?"

Presentation is the process. You can have a presentation without using a deck.

The term you are looking for is Slideshow.

Honest question, what’s the difference?

He is just grumpy and doesn't like the term, for whatever reason.

This is correct.

"Hey are you working on that deck?"

"Yeah, I just need to run to Home Depot and get some more nails"

A deck is that wooden structure on the back of your house. A power point presentation is an electronic file made up of "slides". There is also a "deck of cards", but no one calls a deck of cards just a "deck". Maybe if they called it a "deck of slides", or you know just use a term that makes sense, like "presentation".

No one knows what the hell you are talking about with the word "deck."

It comes from "slide decks", because not too far long ago, presentations were made with actual 35mm transparencies which were slid into a projector, and were carried in decks.

I've always disliked it because a "deck" is stack of small, flat things, canonically, playing cards. A set of PowerPoint slides is not small (they are usually wall sized) and they are not an actual thing I can carry around. I think of a set of PowerPoint slides as a “PowerPoint presentation” or “PowerPoint file”. I guess I could let “slide deck” slide, because a stack of slides would be “deck”-sized, and I assume that sales presentations back in The Day actually were slides of some sort.

To me, a "sales deck" (current title is "The greatest sales deck I've ever seen") implies a stack of playing-card sized marketing material, or a joking reference to your stack of business cards.