Heated beds can provide winter comfort for dogs and cats, and can help alleviate pain and stiffness.
As dogs and cats (and humans) get older, the walls of the blood vessels lose their elasticity, and circulation decreases. Additionally, the fat layer under the skin tends to shrink, and insulation from the cold becomes less effective. Interestingly, a large human study also found that internal body temperature slightly decreases with age, which presumably is true for other mammals like cats and dogs.
All of this means that older pets can be more sensitive to cold than younger animals. Heat therapy - heating pads, heating wraps / packs, and even heated clothing - can bring lots of comfort to our senior companions.