Why does obi-wan not Remember R2-D2 in the OT [duplicate]

This question already has an answer here:

• How come Obi-Wan doesn't remember R2D2 and C3P0 in New Hope? 8 answers

In the PT, ObiWan does interact with R2 but seems to have no memory of him the OT. Also if R2 and C3po had that memories wiped, why does R2 still remember Obi-wan Any possible reasons?