Why don't we have yokes that look like steering wheels?
We Do! It just has been a while since anyone has built a plane like that. 

Many early planes did, notably the curtis biplane comes to mind



As closed cockpits came into be and the modern control set up we see something like a car wheel.


  The cockpit of the Reliant SR-6A shows the love and skill that went into the restoration.



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Yokes then evolved to have a more cut down top like the one seen here (in my favorite plane) the Spartan Execuitve This plane was built in the 30's 



Even later than that the Ercoupe has a somewhat rounded control wheel. 


Also of note the Piper Pacer and Cessna 140 had rounded yokes. After that period most of the big makers moved to the yoke we know and love today. Piper would have a closed top yoke on their early Comanches through the early 60's as well. It should also be noted that early planes (wright flyer etc) had stick like controls. I would assume this was to allow the cable to be mounted far from the pivot for torque reasons although Im not sure (this was for sure before trim). 

Remember in an airplane its all about weight so trimming it where ever you can is worth it. 

In a plane the maximum deflection of a yoke is often no more than 90 degrees so having a full wheel (which allows a hand over hand car style turn) is not necessary.

Orientation is a bit of a concern when flying on instruments but many race cars have center marks on their steering wheels for a similar reason.

For what its worth formula 1 steering wheels see about as much travel as a yoke and are similarly shaped. Some even have more buttons than a cockpit. 


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