I've noticed it with a lot of people too.
The effect of hormone on fat distribution can give us a clue about what's happening. Regardless of if you are a believe or not in Charles Poliquin's Bioprint, the scientific literature is pretty clear on the effect of certain hormones on the pattern of fat storage.
It has been solidly established that there are in fact general effects when it comes to hormones and fat storage.
An hormone (or low level of an hormone) can either increase fat storage centralization or decentralization.
Testosterone and growth hormone decentralize fat storage. So a higher level of testosterone leads to less fat being stored centrally (mid-section, torso, hips) and proportionally more in the limbs.
Healthy levels of estrogen actually decentralize fat storage in females (higher level of estrogen = more fat in the limbs less in the mid-section et al.) but it can actually centralize fat in males.
Cortisol elevation increases fat centralization. So more cortisol = more fat stored in the mid-section and between the organs and less in the limbs.
Insulin magnifies the effect of cortisol on fat storage. For example if cortisol is low and testosterone/GH are at a healthy level, insulin wont lead to more mid-section fat gain. BUT if cortisol is elevated, elevating insulin too will increase central fat storage.
So the logical assumption is that as we age, testosterone and growth hormone levels decrease (which is a fact). That alone would have an impact on fat centralization. And cortisol might tend to be higher too (if you produce less testosterone, you have more pregnenolone left to produce cortisol) then it would enhance the development of that pattern even more. This is also why people gain belly fat more easily as they age: it's not their metabolism slowing down... it's that eating foods that elevate insulin when you have lower testosterone and higher cortisol will speed up fat centralisation.
Activity level, increased stress (from lifestyle changes and more responsabilities) and hormonal changes might explain why fat distribution changes as we age.