Might be a bit weird and gross but ok...
I cannot take a shit outside of my house, or a residence considered *safe* by me. If I have strangers/friends in the house, I will not go take a dump. Nor will I take one in a public bathroom. I'll always leg it home somehow, no matter how much it bothers me.
On my flight to the states a few years ago I had to take a shit at the airport in Vienna. Nope. Not even on the plane. Not even at JFK. Nope. I waited until I came to a clean hotel room. I can say I've been around the world, while having to shit
Also I don't go to the bathroom for dumps, regularly. I can go a week without doing so.