I noticed while I was a Combo-Smite battle report that both players had declared charges against targets that were all the way across the board....so my questions would be: Is a target still eligible even if the charge would automatically fail due to being out of range? What’s the benefit of doing this? Getting the bonus movement, but not making a full run?
You can charge any enemy you can see. It's a relic from the time in which pre-measuring was more restricted. The simplest benefit is that you can cast spells before you fail your charge, but I'm sure there are others.
Also, most light artillery will have SPD 2 base and get +2 movement (not speed) when their crew is nearby, this means they can run 6 (2*2+2), but charge 7 (2+2+3). Note that you can only charge if you actually have a weapon to use in melee, so this may not be viable for all artillery.
Plus, some models have Pathfinder but only when charging, and unless I'm mistaken, failing a charge (even if it's absolutely certain to fail) doesn't prevent you from getting the Pathfinder bonus to help move through difficult terrain.