Someone did a study on that (don’t know why), and it seems that many people have strong opinions on the subject. They’re about equally divided between front-siders and back-siders, and there’s a range as to how important they think it is. People in the middle (like me) don’t much care one way or the other, but some do—a lot. Some have even confessed to doing a roll-reversal when using someone else’s bathroom.

Reminds me of the attitudes toward serial commas. If you write about A, B, and C, do you need a comma after B? As with most things in life, it depends. Sometimes you do need a comma to clarify, but most of the time you don’t—the meaning is usually clear without punctuation.

Still, even when no comma is needed for clarity, some people insist that we shove one in. Others insist that we leave it out.

Why? Don’t know that either.

It could be for the sake of consistency—foolish or otherwise. But I suspect the underlying reason has more to do with the toilet-paper mentality than with any desire for clear writing.

Some people learned a rule way back when, and have trouble giving up their certitude.They're sure their way is the right way, and just can’t stand to see others doing things the any other way. 

Many (I think most) well edited publications do use that serial comma, yet many do not. So do it your way, but recognize that others have the right to differ.