Because a simulator engine is required for simulation. As far as I know Tetramax tool is a pattern generator.
You can write a script which uses the test patterns generated by Tetramax to simulate your design (any form) and then compare the results.
I think a Simulator and a Simulation Waveform Viewer (SWV) are different things.
You can save a waveform to view it afterwards. There are various waveform viewers which will allow you to view such files. But a simulator is a tool which generates those waveform.