Just to kind of go with what DDG and RThomas said...
I've been lucky enough to listen in on two workshops given by a phenomenal agent named Esmond Harmsworth (alas, not so wonderful that he represents horror writers, but you musttake the good with the bad) and he breaks publishing down into very easy to understand terms.
A 120K novel from an unknown author is a
huge gamble when you consider the publishers wil be putting out 25-30% more in costs than they would for most first time writers, and a large chunk of established writers. This is also money they can't spend on something else now, so they can buy two epics or three regular-sized books, which would give them better odds for a sale. The risk also goes up when you consider the epic will cost more at the bookstore, which means it's less likely a random browser will take a chance on this new author. Finally, bigger books take up more space on the bookshelf, so three copies of the epic take up as much space as five or six regular paperbacks, which means LordAnubis Publishing has less books in our three feet of shelf space than KodyBoye Press does, which again means less chance of a sale with less variety.

Now, considering how much trouble it is to convince a publisher to take this 120,000 word novel, you can guess how hard it's going to be to convince the agent who has to convince a publisher to take this 120,000 word novel... That's why most of them won't even spend the time to look at it, because the odds are sooooooooooooooooooooooooo against you. It's not
impossible, no, but it's also not impossible for random atoms in the air to come together and form a lump of gold...
I will say that I struggled with a 125,000 word manuscript for many years, and there's a special nail above my desk for the hundreds of polite rejections my query got. So I pulled out the red pen, took a deep breath, took another deep breath, and after the third deep breath I went through and cut almost 30,000 words from the book.
But I now have letters from agents who have read it.
And, consider you're still in better shape than the guy who walked up to Harmsworth at the last conference, explaining that it was just impossible to cut any more from his 230,000 word mystery novel and he really needed to find a publisher...
