But... they don’t know that it’s false. They are simply giving their customers what they want. If their customer wants to know how the campaign is going based on the same turnout as 2008, why should Joe’s Polling Service say, “Sorry. I won’t take your money. I don’t think the turnout’s going to be anywhere near that. Take your check and shove it.” They sell a service. If someone wants to pay them perfectly good money to run a poll based on ridiculous assumptions, why should they say no?
No legitimate pollster takes such directions when it will make them look like idiots. There is a difference in polls only for internal use (which may very well do what you suggest) and those which are released to the public.
This is not being done at the behest of the media but completely voluntary on the pollsters part. They are part of the media and totally biased.