A Good Home
Though I am still a young woman, I have worked in a few offices in my early career and eaten in many fast food establishments. Generally I have found that the standard of cleanliness is not too bad in these places, but some places, especially fast food restaurants, leave a lot to be desired.
I have always been able to poop in a public rest room if it is clean and I can be reasonably assured that I will not "catch" anything by doing so. If a rest room is filthy, however, or gives me a feeling that somewhere close there is an alien creature about to jump out and attach itself to my rear should I sit down to attend to business, then I would rather forgo the pleasure.
In such cases I have been known in desperation to deposit my poop into my panties to be carried home with care, to where it can safely be washed away. If the toilet I am intending to use is dirtier than my poop is likely to be, then I know that I am safer putting it into my clean panties, which I know to be germ free. (I know that I will not catch anything nasty from sitting on a germ-laden toilet seat.) I know that this may sound like a strange thing to do to some people, but I do have a dread of going into a dirty restroom and bringing out more than I took in.