Amazing how many people respond to a question with "I think..." Or, "no, I'm not running the same software as you, but that shouldn't matter." And obviously very few understand exposure compensation. Simply put, EV or EC or whatever you choose to call it is a shorthand way of affecting your overall exposure when you have locked down some element of the exposure triangle. If you have locked the aperture and the ISO, adjusting EV will change shutter speed. If you have locked down the shutter speed and the ISO, EV will change the aperture. In the latter scenario, you could choose to change the aperture by selecting the menu, or using the dedicated control, or changing the EV. Further you don't have to remember that you have to open the aperture two stops if you want four times as much light, you can simply select EV+2. EV will, in a very simple way, affect the ISO, shutter speed, or aperture, depending on your settings, and it is handy. As to why would you change the EV for technical reasons, here is one reason: Instead of shooting HDR, with limited pre-set EV changes, I shoot three shots–first EV-0, second EV-2 and then EV+2. Depending on the dynamic range of the shot, I may shoot EV+3 to capture some dark detail. The more one learns of the basics of photography–still or video–the more able one is to create exceptional product. We can get beyond the "I think..." world through study and learning and that is a most rewarding experience.