They tend to be 15" or 17". The new 15" Macbook Pro also has better 3D graphics (Radeon Pro 450). It's not as fast as the gtx 1060, but it uses 35W of power in comparison to 120W, and needs less active cooling. Apple generally don't compromise on noise and battery life.

I'm sorry for the snarky nature of my previous comment, but in my experience, all of the suggested alternatives require compromises which Apple are justified in not making. I'm not sure why people think that Apple are obliged to make laptops to suit every use case. If you just want a portable desktop, there are plenty of other options.