This, of course, was quite literally the plan in the original first draft of Episode 1. Why did he change it? I don't even have a theory.
I don't think it was that bad an idea, introducing Anakin as a slave on a backwater planet could have laid some very interesting groundwork for his turn to the dark side, rather than introducing him as a Jedi apprentice.
The Vader of the OT was all about order, justice etc, Anakin being enslaved by some gross junk dealer and his mother being tortured and killed by wild savages on a lawless, gangster planet that the Republic doesn't care about...it makes perfect sense that someone like him would eventually reject the uncaring and dogmatic Jedi Order in favour of a just Empire that brings the rule of law to every corner of the galaxy. Unfortunately George made some really dumb decisions like:
1. Making Anakin 8 years old, instantly limiting the range of emotions he could show.
2. Anakin's life of slavery seems fine, he gets to play with his friends, live with his mum, race cool cars, etc.
3. Casting a teenage Natalie Portman opposite him
Anakin should have been of a similar age to Luke in ANH and been much more rough around the edges. A kind-hearted person but one who has a burning resentment inside and who despises being trapped under Watto's ownership. Then it's only logical that meeting Padme, Qui-Gon etc would push him to finally break free, join the Jedi and become somebody. What we get in TPM is a totally oblivious, saccharine Anakin who has no real input to the story and is just ushered from place to place by Qui-Gon. His relationship with Padme is non-existent and it damages the whole trilogy as Anakin never really feels fully-fleshed out due to George wasting a film on him as a kid.