I'm generally hesitant to a) choose a stranger to use my camera/iphone because hey, I don't know them, and there's a chance they could run off with my camera, and b) bother a stranger every single time I want to take a group shot.
I'm generally the photographer on our trip which means unless I make a point to take a selfie or ask someone to take a photo, I don't get in the picture too often, which is a bit sad. When you look at your family's photo albums, do you want to see photo after photo of only your kids, or only your kids and your husband? No, you'd like to be in them too. Having to hunt down someone to take a photo wherever you want one isn't really appropriate. It's their vacation too, not just mine. I see nothing wrong with the proper use of a selfie stick for a group shot.