Hands age, just like the rest of your skin. Sun exposure can leave skin looking leathery and weathered. What happens when you just use a daily SPF on your face? Your neck and hands show the wrinkles, sunspots, and age. It looks pretty silly.

The skin on your hands is more likely to be damaged, than say the skin on your forearms. This is due to exfoliation from just washing your hands more often than the rest of your body, and simple tasks where dead skin is sloughed off through rubbing and touch. The washing of hands a few times a day, is also why they put SPF in handcream. You don't wash your face a few times a day at work, and hopefully you applied some sort of SPF to your face at home.

The sun damages your skin during the winter, as well as in the summer. I live in Florida, where you wind up with a slight tan from just driving, walking in and out of buildings etc.. It is importent to protect your skin from UV rays, not only for aestetic reasons, but for your health. Skin cancer is not fun. Like they say, wear sunscreen.