Who says that we don't need anti-wrinkle cream before 40? We are entering a pre-aging in our late 20s to mid-30s! If you don't realize it, just look at the mirror and you might notice lines around your eyes and mouth or even dark spots from sun damage.
Pre-aging may be the most depressing moment and a very very bad news for women when she got that at her early 30s. So, thats why we need to keep our skin younger by using anti-wrinkle products even if we haven't hit 40s.