What is it about being in the silence of their own thoughts that makes people uncomfortable and uneasy??

Yesterday I was traveling on a bus. The driver had the radio on, and some loud dancehall music was playing...
*Enter annoyed Rb*
Rb: Driver, yuh can't find something else to listen to? Find some news or something nuh!
Driver keeps driving. Rb feels ignored.
Rb (raising voice): Hey driver!! You nah hear me?? Me say find some news or something fi wi listen to!!
Driver turns off radio. Enter annoyed 'other passengers'.
Other passenger 1: So wait, driver, a one person you a carry? Turn on back the radio man!
Other passenger 2: Driver, a more than one a we in here, enuh. You ago make one woman make the rest a we vex? Tun on back di radio. Me nah drive go St. Mary inna silence.
Other passenger 3: Yow driver, majority rule. Run di music.
Driver continues driving. The radio remains off. Other passenger 3 beside Rb turns on her cell-phone and starts to play some music.Rb sighs, starts to silently chant and petition heavenly intervention. Other passenger 3 puts phone close to Rb's ear. Rb starts to chant and request divine intervention under her breath. Other passenger 3 starts to flip aimlessly through her songs, then with a loud hiss-teeth, turns off her phone.
*Enter PERFECT SILENCE for the rest of the journey home, and a happy Rb.*

What is it about being in the silence of their own thoughts that makes people uncomfortable and uneasy??