I think Obi-Wan believed Anakin was (literally, biologically) dead when he dropped off Luke, and that Owen would have also. And that it wasn’t until later that he learned Vader survived. It explains why they thought taking Luke there was a sane idea and more comfortably fits in with what we hear from Owen and Beru in ANH.
The most reasonable thing to assume would be that Owen and Obi were lying to Luke: Tatooine was not the birthplace of Anakin (or his wife). Obi and Owen fled there with the infant Luke (the furthest place from “the bright centre of the universe”) to be in hiding.
Of course the PT screws all that up.