Almost never.
On the rare occasions that I need to punch a hole in leather, I use a pliers-style leather punch tool. They make very clean and accurate holes and I keep the tool in my shop. I just never ever have the need to punch holes in leather when I'm out and about. Of all the blades on all my knives, it's among the least used and I carry an Ulster camper quite often, so it's not like I don't have it available to me.
The cap lifter/screwdriver blade on the other hand is way high on the list of frequently used non-main blade tools that I use.
Most frequently used non-mainblade tool is folding scissors though. I know that may not be manly to admit that, but I end up keeping a small SAK (which I dislike in every way possible) or small Leatherman (which I can barely stomach) for the scissors alone.
Someday, somebody is going to make a scout pattern knife with the leather punch replaced with scissors. I'd be all over that like a fly on honey.