The reason is that silicone hydrogel lenses, while extremely healthy for your eyes, tend to attract a buildup of protein deposits. Rubbing your lenses at night will reduce this buildup and keep your lenses cleaner longer.
Even if your lenses are not silicone hydrogel, rubbing them nightly should still be part of your routine.
Have you ever read the instructions for a “No Rub” solution? They instruct you to rinse each side of each lens with a steady stream of solution for 10 seconds. That is 10 seconds times 2 sides of each lens, times 2 lenses. What they want you to do is rinse your lenses for 40 seconds with a steady stream of solution? And how much solution are they expecting you to purchase? And how many people are actually doing that?
Rubbing your lenses only takes a couple drops of solution. After washing your hands, place the lens in the palm of your hand with a small puddle of solution. Rub your lens from the center towards the outside for at least 10 seconds. Never rub your lenses in a circular motion as this can tear and warp your lenses. Then simply give the lens a quick rinse of solution and place it in your case.
Always use clean fresh solution to store your lenses and allow them to soak for at least 6 hours for optimal cleaning.
That is all there is to it. The next morning you can rest assured that the lenses you are placing back on your eyes are clean and healthy. You only get a couple of eyes in life, do everything you can to keep them healthy.