It has to do with the number of taste buds and touch fibers on your tongue. The fewer you have, the less sensitive you are to the taste of food. Apparently, this arises because people who are “taste blind” carry a mutation in the gene that controls a factor (gustin) involved in taste bud development.
A recent study examining people who are “taste blind” compared with people who are “super-tasters” showed that people who are “taste blind” tend to consume more calories. Of course, this is what you’d expect considering that they’re less sensitive to subtle tastes and thus tend to prefer rich foods.
—I learned about this fact from: Tepper, B.J., et al., Greater energy intake from a buffet meal in lean, young women is associated with the 6-n-propylthiouracil (PROP) non-taster phenotype. Appetite, 2011. 56(1): p. 104-10.