I posted this in a earlier thread and figured id throw it in here as well. T
he simplest answer is running backs hit the point of attrition faster. In part to your theory of everyone seeing them going. but usually leagues start 1qb and 2rbs.
There are only 32 qbs so even in a 10 team league, there will be more than enough qbs to go around and you can "wait" on one.
RBs however dont have that ratio. There are actually less than 32 starting rbs because of RBBC. So in a 10 team league, 20 rbs will start every week. When you consider there are always RBBC teams, 20 picks is almost all the starters.
So as an owner, when drafting, you take a calcualted risk. You might miss out on the QB you want by taking a RB in the second round, but if you take the QB, lord knows what youll get at RB.
However, in 2qb leagues the numbers come closer in terms of overall worth for rbs and qbs. I love two qb leagues and always "try" to grab 2qbs and 2rbs with my first four picks. Of course if I dont like what im saying at a certain pick and a stud wr is there, then I may have to adapt.