Actually there used to be another, more important reason:

Back in the old days, automatic transmissions accelerated pretty slowly. It was not possible to accelerate normally – or what we thought to be normal. No one in their right mind would pay ~5–10 % more (automatic transmissions used to be expensive) to get a lame car and annoy everybody at every traffic light. I don’t know when automatic transmissions got as fast as manual shifting, but this memo hasn’t reached Europe yet.

And, last but not least, and only still valid argument: automatic transmissions are still more expensive than manual ones. Why should I pay extra money for some fancy tech with no extra benefit that takes away my illusion of control and feels horrible to drive?