Why do NBA players have towels on their laps on the bench during timeouts?

Answer 1

NBA players sweat a LOT during the course of a game (obviously). The "lap towel" serves 2 primary purposes.

1.) It helps to dry the sweat and cool the temperature from the upper-legs (thighs) because of all of the energy that NBA players extol from usage of their legs. This allows the thigh muscles too cool off at an athletically appropriate pace so that the leg doesn't become over-taxed and/or cramp up.

2.) The towel also helps to prevent sweat-induced odors from wafting upward from the players' groin areas (aka: "meat lockers"), thus, helping to prevent the bench area from smelling like a big salty nut sack. [Consider it the NBA's "Dirty Little Secret" lol]

Hope this helps!