Why do Hebrew clocks run clockwise, not counter- clockwise?

Some do, but I wouldn't lose sleep over this question. FYI, the clock
on the tower of the Prague Jewish Community Center uses Hebrew letters
and runs counter-clockwise.

Most clocks use Arabic numerals, another right-to-left language. The
real question is why Roman numeral clocks don't go the other way.

Note that the direction of the written language has nothing whatsoever
to do with the way clocks run.

The clock is a mechanical timepiece modeled on its predecessor, the
sundial. North of the Tropic of Cancer, the sun affects the sundial in
the following way:

• Sun rises in the east: shadow falls in the west.
• Sun, at noon, is south: shadow falls in the north.
• Sun sets in the west: shadow falls in the east.
  
  The shadow moves in a W to N to E rotation, which is what we call
  "clockwise." When mechanical clocks were invented, this rotation was
  duplicated. Regardless of the direction of your written language, the
  clock hands move the wrong way half the time!
  
  South of the Tropic of Capricorn, a sundial moves counter-clockwise,
  and between the tropics, the motion of the shadow depends on the time
  of year. Had the clock been an invention of South American Indians or
  Southern Africans, "clockwise" would likely mean the opposite
  rotation.