rate of lucky coincidences
Lucky coincidences are not evenly distributed, neither across time nor population.
Some people are better at paying attention to peripheral details and making spontaneous associations. These muscles can actually be trained and one can get luckier with time and effort. However, as you age, you will have less energy, time and desire to spend on activities where these muscles can be put to work. (e.g. Travelling, going to conferences, meeting new people) In other words, your rate of lucky coincidences is programmed to diminish across time.
PS: On a related note, see the post creativity and ambivalence.