Abit of research (autotrader) shows that there are more autos only in the 3 litre engine size for 3 series cars. I'd say thats down to the fact that an auto suits a bigger engine, in which case most people that buy 3 series are pretty clued up. Percentage wise its 66% autos to manuals.
And a manual suites every engine... the only good autos are DSG based that do not **** about when you use the paddles but instantly do as you ask them