Supply voltage of LM741 with Virtual Ground
Almost certainly the Proteus model for the 741 does not correspond exactly to the real thing. Particularly, it does not model the schematic of the IC. Rather, it uses a set of idealized components which have values (gain, frequency response, bias and offset currents, etc) chosen to correspond to the published data sheets. As a result, it works just fine as long as you operate within the published limits, but does not accurately reflect what happens when you operate outside those limits.