In the case of 3PO or R2 units, you'd be right. But power droids in the EU are depicted as having extremely limited intelligence (since they're basically walking batteries, this makes some sense), to the point that a crimelord was once able to order a power droid to walk into a room filled with his rivals and tell it to overload its mini-fusion generator...
Restraining bolts aren't the true sign of droid slavery though, that's the memory wipe. It's not just a way of keeping secrets, as Organa thought when he had C-3PO scrubbed at the end of RotS... it's been stated as a routine measure against droids expanding beyond their programming. Some owners allow this - R2's owners have often found his "experience" has enhanced his abilities and value this - but it seems that many fear droids will begin making decisions outside the strict parameters of their factory settings.
