I recently noticed this in the NFL, why is it that when the QB is sacked the R stops the clock?

I don't really know of the rational, I think it may have to do with giving the recievers a chance to come back to the huddle.

Snake-eyes - You're on the money. Markbreit said the same thing in his column.

However, this does not apply in the last 2 minutes of either half.

[Question]
"Being a high school official, I've never understood the rules surrounding the clock being stopped when the QB is sacked. What is the rationale for stopping the clock in this situation, and what conditions are needed for the clock to actually be stopped? --Mark Dexter, Plainfield, Conn.

[Markbreit's Response]
This rule only exists in the National Football League. The reason is to allow the deep receivers time to return at or near the line of scrimmage before the clock starts again. Several years ago, this rule was modified. Now the clock is not stopped on sacks during the last two minutes of each half."

http://chicagosports.chicagotribune.com/sports/football/bears/askthereferee/cs-051228askjerrymarkbreit,1,1174018.story?coll=cs-bears-asktheref-headlines

I remember that they would stop the clock until the next snap but now they restart it on the ready if it is stopped for the sack.

I wonder whether the rule was changed to allow the stoppage before the 40 second play clock was instituted. If so, it doesn't seem to make sense any more. If you have a 40 second play clock for a 50 yard downfield pass, where the line needs to motor to get to the new line of scrimmage, I don't see why you can't have the same with a sack.

I bet it usually takes no longer than 15 seconds for the ready anyway, so the result is the same either way. Just treat it like any tackle in bounds.