To pry things that don't require the leverage of a full-sized or extra long prybar. Or self-defense. Or to open a bottle. Technically, the bottle opener on my keychain is just a very small prybar. I've used it for actually prying small electronics apart since I don't have one of those kind of spreader/spatula things made for that.
I have found the usual small prybars useful, but I have since discovered variants like this:
It provides a much better grip and the curve give it a lot more leverage. I've been surprised at how much more effective it is than straight bars of a similar size. (This one was made by Teale Designs on Etsy.)
I have a Gerber shard and I don't think I've ever used the prybar on it. I've used the bottle opener a ton and to a lesser extent the two screwdriver ends.
I use mine exclusively for its prybar but it's hardly my EDC. It's handy around the house for the jobs not requiring anything bigger. If I'm caught unprepared in urgent need of a prybar of all things, I already must have screwed up in an amazing manner.
I have a little pry tool keychain thing. It has a bottle opener and flat head on it. The pry bar bit can also act like a big flat head for things that have a coin slot meant to tighten or open it. It's not meant for nails or opening wooden crates.
Really it's useful for any poking of prying that you shouldn't be using a knife for but have a strange urge to. Also a package opener if people around are nervous about knives. The utility knife thing with a bit of crowbar glued to it probably doesn't comfort others as it looks like how someone would design a tactical box cutter.
Any weird little prying/scraping/poking jobs I don't want to use my knife blade for either for fear of damage my knife or the surface of whatever I'm poking at.
It's opened some paint cans, pulled a few nails, probably the best use though was when I needed to pop open the dome light in my wife's car to replace the bulb, didn't really want to be stabbing at the headliner with a sharp knife
It's not an everyday use thing, but I find enough excuses to use it that I don't regret it.
I got impulsive one day and decided that I absolutely just had to pull the old nasty carpet off my basement stairs. Since this was spur of the moment I decided to use what I had on me, which included my small pry bar.
It worked well on loosening the wooden strips that held the carpet as well as some random staples that were there for...some reason.
I've found a few scenarios where I can use it, even if it's just prying something open and I don't feel like marring my pocket knife. While I don't have a specific use case for my pry bar or half my tools for that matter but it's always nice to have the bar just in case.
Being able to pull up or peel something without peeling back your thumb/finger nail is kinda nice. I don't carry a specific pry-bar, but some things I carry have a pry-bar-esque utility that is super handy.
I needed one to break into drawers in these carts were were decomming at a previous job like 10 years ago. That's really the only time I can think of where I couldn't do what I needed to do because I didn't have one on me. Other than that I've gotten by without it.