Ask HN:Why do in-ear plugs have left and right marked on them?

Is there anything different in how the two plugs are built?

Is there any difference in how our left and right ear works?

I find that due to my obsessive compulsiveness, I waste a few seconds every time I use them in making sure that I am putting them on correctly!

EDIT: In addition, does it have an effect on your hearing experience if you put the left ear plug in your right ear and vice versa? If not, then why bother marking them?