The other possibility is that as a large number of shareholders...

The other possibility is that as a large number of shareholders simply won't bother either because they've lost interest and/or the amount involved is trifling. There is no underwriter as such but a fee will be paid in certain circumstances. Suppose someone with an astute perspective scoops up the forfeited options and builds a handy stake ahead of whatever is on the cards for next year without pushing the price up in the process. (not really a conspiracy theory but could easily be worked up)