Why don't they make a transparent steering wheel for cars?

In order for a manufacturer to make anything, they have to make enough of them for it to be worthwhile. A transparent steering wheel is more of a novelty and wouldn't sell enough to make it worth manufacturing.

It shouldn't be that hard, however, to get one made. Just needs a mold or the right plastic block to carve it out of. I'd go with the mold however, as molded plastic is less brittle than block, as block actually does have a kind of grain.

Be aware. I'm not sure about this, but I do have some experience with plastic. It's possible that the constant exposure to the extremes of temperature that can occur in autos could make the plastic brittle, or may discolor it.

All in all, though, I'd say it's certainly worth a try and would definitely give you a 'different' touch in a custom car.

Actually, I'm BSing you. Transparent steering wheels were quite common in the 50s and 60s, especially in Pontiacs.

Restored Pontiac wheels

http://www.qualityrestorations.com/pontiacclear.html