Targeting doesn't always mean weapons, especially when dealing with sensor systems, which oddly enough, is exactly what we're discussing.
Better grade of sensors means longer detection range, which also includes detecting silent running ships farther out(that can be very important depending on what you are doing), and you target a ship to see what it is, since your sensor display only shows you WHERE the ships are, it doesn't tell you WHAT the ships are, their status, or what they are carrying, for that, you need to target them.
My Anaconda, A sensors, I can target something 7km away, but my rails and lasers don't do damage that far out by any means. I can see the sensor contact, target it, and see what it is and decide if it's a threat or not, kilometers farther away then it can probably see me, since so few people use A class sensors. Is it worth the weight, price and power drain? That's up to you, but generally, anything that gives you an advantage is a good thing...