Have you tried cleansing twice? If you're not already a convert then you might be shocked to find that a second cleanse reveals yet even more make up on your cotton pad.
We really do need to remove all of the make up and grime which acrues on a daily basis. When I lived in London I really noticed the pollution on my skin, but even in a quieter city when I walk near a dirty road I can feel the dust settling onto my skin. So it's there, and it needs to be removed completely so that your pores can breathe and your skin can repair overnight.
Cleansing twice is worth the time and the expense of extra product and cotton pads. Really work the cleansing product into your skin paying particular attention to the jaw line, nose area and forehead, where congestion tends to be more of a problem.
This rule extends to hair care too. Shampooing twice and rinsing really well extends the life of your hair between washes. It's a lot easier to wash hair the second time round as the product goes further. Cleanliness is close to Godliness