The Pokeys57CNC feature list includes the following point:

"support for up to 100 sensors, that can be connected to I2C bus, 1-wire bus or on the general purpose analog inputs,"

I guess most of the people (maybe Im wrong) will use the board in combination with Mach3

Is there really no possibility to access I2C and 1-Wire values from Mach3?

Greetings,
Max

Mach can access values from Pokeys and Pokeys can access values from Mach.  Its in the manual(s).

As Max pointed out, most users won't be using sensors values at all, so there was no real necessity to support them directly.
Since Mach4 can communicate with the PoIL diagram (created using PoBlocks and run in the device), one can read the sensors in PoBlocks and forward them to Mach3 via 'PoIL shared slots'.