Total number of pixels

What am I missing? Why is a script necessary to multiply w x h?

Simple script snippet:

try{
    var originalRulerUnits = preferences.rulerUnits;
    preferences.rulerUnits = Units.PIXELS;
    var h = app.activeDocument.height;
    var w = app.activeDocument.width;
    var t = h * w;
    Window.alert(h.toString() + ' pixel height\r' + w.toString() + ' pixel width\r' + t.toString() + ' total pixels');
    preferences.rulerUnits = originalRulerUnits;
    }
catch(e){
    Window.alert(e + ' Line: ' + e.line);
    }

If the image is flattened, then Image > Canvas Size or even Image > Image Size or the Properties or Info panel can show the current pixel width and height. The histogram panel will list the width x height in pixels.

If there are layers, their content may be smaller or larger than the canvas and can be found via Properties or Transform or scripting bounds.

Yes, this can easily be scripted, but what do you need to do with the total pixel count?