system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Are R2D2, C3PO, HK-48 and the other "Protagonist droids" more than the rest of the droids in the SWU? Are they more sentient?
gpt
The way droids are programmed leaves room to develop sentience via an extended version of the "personality development" part. This takes time, however. 

To forestall this, most droids are mindwiped with each sale, effectively giving them a factory reset. C-3PO's personality would thus have come from his work with Princess Leia Organa, even though he was much older.

R2-D2 was a special case, having escaped all mindwipes he would have been subjected to.