I imagine Sarah doesn’t want to subject herself and her kids and Todd to a continuing media circus, depositions, court appearances, attorney fees and on and on!
Just guessing though!
If there were charges, they would be pursued by a local prosecutor as criminal charges, not a civil law suit, tho the Palins could sue for damages, i.e., cost of medical bills, pain and suffering, any lost time from work, that type of thing. But the primary ‘charges,’ i.e., assault, theft, are criminal. Someone would have to “PRESS” charges. The Palins probably figured, as you note, that the aggravation wouldn’t be worth it to pursue either the criminal or civil cases.