Light twins not using contra-rotating propellers

Recently, Mxsmanic posted:

Mark Levin writes:

As was pointed out to me the Beechcraft Baron does not use
contra-rotating propellers. A bit of research showed me that most
U.S. built light twins do not use them either.

My question is why?

My guess is that the market for mirror-image engines (the most
straightforward implementation) is too small. If you don't use mirror
images, you have asymmetries in the powerplant engineering.

Probably not the market, but the cost of maintenance, quantity of
available parts, and other things mentioned in this thread are reason
enough to warrant the practice.

I do wish that things were different. I consider the effects of
P-factor and torque to be design defects.

A design defect is a problem caused by some aspect of the design. I don't
know why you would consider the effects of propeller propulsion to be
"design defects". They are simply aspects of that type of propulsion.

Neil