I get that, with infants, you truly don't have a choice to have the child wait a bit. More often than not, it is easy enough for me to remove myself if someone isn't being as discrete as I prefer. I've been lucky that the only babies I've spent time around (my friend's two kids) have apparently been very easy to swap back and forth from breast to bottle, and she always has a bottle available in public.
However, I think there is a point, as people return to breast feeding later into the children's lives, where you can say "We will do this in a few minutes, let me finish up here first" to the child. I've seen kids as old as five breast fed in public or semi-public places. If that's your thing...rock on, I suppose. I'm not sure where that cut-off lies, as I've never had to deal with it, but I believe there is a cut-off there somewhere.