10 Dumb Decisions In Star Wars We Can't Forgive
6. Episode I - The Origins Of C-3PO
Repeat this sentence very slowly to yourself, and you'll understand why it sounds stupid:
"Darth Vader built C-3PO to help his mum around the house."
In Return of the Jedi, when Darth Vader has his helmet removed and we see a scarred and dying man underneath, we not only see him as a vulnerable figure, but we're interested in the idea of "how did he become like that?". The mystery and the story behind how a man ended up in that suit is something that just has to be told.
No one ever looked at C-3PO or R2-D2 and thought "I wonder who built them...". They're robots/droids - built in a factory somewhere and given mild personalities to serve Princess Leia. That's all we needed to know.
The plot-holes for future films aren't even the worst thing about this reveal. When we're first introduced to Anakin he's asking Padme if she's a literal angel because of her beauty. Something a very young child would do.
The introduction of "Threepio" would have been a fun nod to audiences if he as waddling around in the background, but to have Darth Vader be the one to build him when he was a kid is just pants-on-head dumb.