PIC16F1503 CLKOUT doesn't work
I think the MPLAB SIM documentation sums up the issue perfectly:

MPLAB SIM only simulates to the register level, not the pin level,
e.g., RB0 represents the value in bit0 of the PORTB register, not the
value on the pin named RB0.
This makes sense as the simulator is a software model, and not actual device hardware.

Since CLKOUT is based on the chip hardware and isn't a SFR, it won't be simulated.