Good question! I also wondered why, but now I noticed that some cosmetic companies propose after-shave balms as body/hand lotions for men. After-shave balms and body lotions are pretty similar products, as they are scented oil/water emulsions. The only downside is the price. Usually the after-shave balms are carried in small bottles, and if I used the balm as body lotion, a bottle would last for just 2 applications.
So... I use unscented body lotion or massage oil and then I spray my SOTD, so that it will last much longer.