The moment we make a robot capable of reliably fetching a sandwich it will no longer be ethical for us to order it around (at least, not without paying a salary).
But to be precise: at that point, it will no longer be ethical for us to order it around. We will have to resort to asking politely or to bargaining, such as giving it some form of salary in exchange for fetching sandwiches.
'My usual.' or 'ham salad, easy on the mayo.'
Then the robot has to cross the street, queue at the sandwich store, discover that they're fresh out of mayo, or whatever, and has to decide what to do next. Should it contact you for new instructions, take the initiative and visit a different place, buy ingredients and prepare a snack personally, or any other of countless possibilities? Any of which may involve handling new, unanticipated phenomena.
Thus fetching a sandwich, reliably, is a creative task, and any entity capable of doing it has achieved human status.
Robots in Futurama are near human status. Real robots (including the one you described) are not. Fetching a sandwich as a robot is an algorithmic task.
Why should we go out of our way to build robots with similar ideas of what is pleasurable to us?
Well, now that you think of it we are all in a way programmed to enjoy certain things through classical conditioning.