Conventional wisdom will tell photographers that highlights are scary, and should be avoided at all costs. The 'blinkies' highlight warning becomes your new best friend, and you are led to believe that a white spot in an image is punishable by death. You are encouraged to underexpose, because you can lift the midtones in photoshop later.

There are problems with this. Digital camera sensors are not really designed to record darkness. They record light. This means that a bright area of a picture contains more data than a dark area.

 

 

So if you stop filling when you reach the shadows, or the darks, you're not getting the whole picture. If you use photoshop to fix this, you're going to have to water it down a lot. The shadows will be noisy, and the bright areas will look banded, because the histogram has been stretched out. This creates gaps, and the computer has to make up data to fill the gaps, based on it's best guess.
 

The glass on the left is nearly a pint, but you wouldn't accept it. Because you're not getting everything you paid for. If you don't use the top end of your sensor, then you're not getting the best from it. The glass on the right is still a pint, but there's a little extra. You would still call it a pint.  And all you've lost is the very brightest stuff at the top.
There is limit though, and any more clipping would just be a waste.

If you try to look at the sun, or a lightbulb, then you'll squint. Your eyes will hurt, because they have their limits. Those sorts of highlights should be clipped, or the rest of the shot will look un-naturally dark. But try pushing it a little. Shoot RAW files, and when you think you've got the right exposure, try taking another shot a stop or two brighter. Double your exposure time, or your ISO, or open up your aperture.

Compare the results when you get back to your computer, and you'll probably find that your shots are much smoother and more detailed than they were before, particularly in the shadow areas.
There's no harm in taking out the bits you don't need, but you can't fill a glass from your table.