This is How They Wiped Themselves in Ancient Rome

In large parts of the world today, proper etiquette dictates eating with your right hand and drinking with your left.

As is often the case with respected traditions, there is a practical, common sense reason behind it that may not always be fully appreciated or understood --- especially by western bourgeoisie.

In keeping with the above, proper bathroom etiquette likewise dictates using the left hand to wipe --- and additional tools may not always be available --- and it has been this way for centuries.

Even today, everyone doesn't always have the luxury of toilet paper, running water, bidets or even wiping instruments. In which case, you use what is most handy.

They may not have been great at wiping their butts, but oddly they may have been better at birth control than we are

https://en.m.wikipedia.org/wiki/Silphium