Plenty machines run unshielded stepper motor wiring, but those machines will also likely be running 24VDC control circuitry with some differential signals for anything that runs at low voltage.

The primary driver behind shielded wiring on hobby machines, is due to them often using low voltage/high impedance (sub 5V, with only mA of current) control circuity, which is very susceptible to EMI. The EMI from stepper motor wiring can be enough to cause noise problems on those machines.

24V control circuitry is far more resilient, and for most 24V systems you could probably run a HF welder next to the wiring, and not have any issues.

However, the bigger question is why do you need NEMA34 motors?
A suitably geared NEMA 23/24 motor will likely give better performance than NEMA 34, especially if you're not using high voltage drivers.