Fetching lunch,,,not a big deal once in awhile. If it becomes daily and it impacts my gas to a serious extent, not ok.
BUT I do think that the Phrase "It's not my job" definitely has its place in certain circumstances. For instance I used to be a home health care aid and one of the girls who worked a with me at a nursing home ( we were both private pay aids for daily visitors to the place) had a client who wanted her to change adult diapers for the person her client was visiting, toilet and clean her, bathe her and so forth. Yes, it is her job to do that for HIM, not for a third party. It was a great deal of liability for her and she told the client "Not my job" several times.
I think there is a bit of sucking it up to be done on any job...but sometimes you have to draw boundaries at work,too