If you have a choice of several cards, you often want to pick the one that is the only one of a particular suit, so you have the best chance of making a flush as well. Each of those cards can participate in 5 different straights (E.g., a 7 can be involved in 76543, 87654, 98765, T9876, & JT987). The answer is that you have a better chance to make a straight with a singleton 5-T than any other cards.
Faygo's right as always.But you might question why a 5-T instead of a 2-4,J-Q etc.
