built-in phono stages -- good idea?

It seems to me that the best location for a phono stage is at the tone arm wire end -- in the turntable. My thoughts:

This would bring the following benefits to its performance:
Elimination of the sensitive and susceptible phono cable
Reduction of the need for a balanced phono stage
Reduction of noise without the need for balanced design -- half of the battle is won already.

Both are significant advantages, I think. But this puts some limitations on the design of the phono stage:
Needs to be very compact solid state design, probably SMD. Access to loading options and mc/mm switching need to be thought out and accessible from rear or underneath. Again, both doable.

Why don’t we see this more often? Your thoughts?

Wouldn't the shield box easily shield from the motor?
Wouldn't the shield box easily shield from the motor?
It depends on the material. I've found over the years that ferro-magnetic materials in the chassis can affect the sound of the product. Especially when using a single-ended circuit though, placing it near a hum field like a motor seems unwise.
B&O made a couple table with a built in phono section. I owned one and it wasn't noisy, sounded pretty good all things considered.