I believe that travel calls for a common sense approach that assumes you will be the victim of a pick pocket.
The only remaining question after that is how to protect yourself by, at the very least, absolutely protecting key items such as cc, id's, and your any stash of cast that you might have.
We see it so often when we travel. People hanging purses, etc on the the back of chairs in outdoor cafes. People flashing wallets full of credit cards and money in stores. People leaving purses, bags, cameras etc. on the ground at the foot of their chair in outdoor dining venues. Worse, people dropping backpacks etc to turn around and snap a photo or a selfie of themselves or others.
You need to exercise a certain amount of basic common sense. You need to be aware of what can happen. You need to be aware of your surroundings. Thieves are on the lookout for those who do not practice these basic precautions. Even if you do practice all of these and more you can still very easily become a victim.