The droids couldn't have the same emotion that people got out of R2 and 3PO, we didn't any views from their perspectives and all we were able to see was them getting shot, not to mention that if they were to be given a lot of character and what not, it would have been even more expensive for the CIS that they just couldn't afford, unlike the Republic who had all the money in the galaxy (exaggeration) to spend on well performing soldiers.