There is a danger that robots in a game (or in fiction) may appear as no more than a de facto slave race. You can either ignore the parallels to real world slavery, or bring them out as a potential social issue within the game.
Some gamers don't care for transplanting real world issues into games and just want to escape to a world of heroic adventure, but others may be intrigued by exploring such issues within a game setting. Try to check how your players feel about such things before you suddenly start having their pack mules stage a revolt.
GM: There are four Imperial TIE fighters chasing you.
Han: I fire at them! Pew! Pew! Pew!
[SFX]: Pow! Pow! Pow!
C-3PO: I feel so useless. What can I do?
Han: I'll have a hot chocolate. White marshmallows only, no pink ones.
R2-D2: Because you're too manly to have pink ones?
Han: It'd be like having a straw in my Peach Breeze.
C-3PO: I'm not your maidservant! Get it yourself!
Han: Sorry, I meant in the game, Sally.
C-3PO: So did I. Droids aren't slaves, you know.
[SFX]: < eevoo bedoop doip >
R2-D2: Preach it, cyber-sister!
C-3PO: In fact, we hired you, so actually I'm your boss.
Han: So... you want pink or white marshmallows?
C-3PO: Just shoot the fighters!