Follow the money. Political campaigning is a multi-billion dollar industry.
The Media is a large recipient of those billions of dollars.
The Media has a vested interest in promoting close elections so the political campaign begs donors for more money to spend on Media advertising.
Same thing is true for the pollsters. If the pollsters accurately polled, there would be no interest by the campaigns in conducting new polls if the current poll showed them far in the lead.
>>The Media has a vested interest in promoting close elections so the political campaign begs donors for more money to spend on Media advertising.<<
I believe you are absolutely correct.