The reason why is very simple. Simple enough that they admit it themselves, before the list is even seen.
The hardest part was deciding how to rank them. Do we look at just this year? Do we look at their careers and their body of work? We decided it would be a mixture of the two, that we couldn't completely ignore a veteran with a history of great success having a subpar year.
The hardest part is coming up with a method of evalutation. Really? I can give you a ton of ways of evaluating QBs (in no particular order, as Scouts Inc. would prefer it):
yards per attempt
drawn out of a hat
drawn out of a shoebox
alphabetically by last name
alphabetically by first name
alphabetically by middle name
color of teams home jersey
and last and most definately least:
The point is, if you are going to make a list, you need to have criteria. "A mix" of the criteria does not cut it. Then you just have subjective dribble.