1. Acoustical problems in the room are more accurately measured in the time domain.  This type of analysis provides information about the direct sound and the effects of reflections from room surfaces.  This was a departure from traditional EQ methods that only looked at data in the frequency domain.
2. Measuring in a single location does not capture sufficient information and often results in equalization artifacts.  Multiple measurements are required to capture the spatial distribution of acoustical problems, particularly in the low frequencies where the problems are more serious.

bitflipper

Why not any of the other 763 (ok, maybe more) equalizers any one can choose to try on a playback system? Could be fun.

With careful measurement, you can actually do it with the Sonitus EQ. I've done it, and measured and confirmed the benefits. As long you're not working in a drain pipe, and as long as you do only cuts, it works. As with all room EQ, it works at the mix position only - other points in the room may sound noticeably worse.

However, I don't like the idea of using a plugin for this. It's extra overhead, something you have to remember to include in every project, something you have to remember to bypass before exporting, and doesn't work with all your audio software. 

So instead I use an inexpensive hardware parametric between interface and speakers. It's on all the time, doesn't interfere with exports, applies to all audio software, and imposes no overhead on the computer.