Just pasting an AI answer here. Thought it could be interesting to compare with the actual answers real people share:

Okay, let’s examine the available information to address your questions:

The placement of the engine in a car (front, mid, or rear) has various advantages and disadvantages:

Front-engine cars:

• Advantages include good traction, efficient energy transfer, and more cabin space since the engine is not in the cabin. [1]
• Disadvantages include less-than-optimal weight distribution, which can affect handling and performance. [1]

Mid-engine cars:

• Advantages include excellent stability and handling due to the central weight distribution. [2][3]
• Disadvantages include less cabin space, more complex design, and difficulty in regaining control if the car starts to spin. [4]

Rear-engine cars:

• Advantages include excellent traction and handling, especially in snow and ice conditions, due to the weight distribution. [5][3]
• Disadvantages include less stability and the engine being in the rear can make the car harder to control. [5]

As for why not every car has full-wheel drive (AWD), the main reasons are:

Cost - AWD systems add complexity and cost to a vehicle, making them more expensive to manufacture and purchase.[6]
Weight - AWD components add significant weight to a vehicle, reducing fuel efficiency.[6]
Packaging - Accommodating an AWD system can be challenging in terms of vehicle design and interior space.[6]

So in summary, the engine placement and drivetrain configuration involve trade-offs between performance, handling, cost, and packaging that automakers must balance based on the target market and intended use of the vehicle.