Why want the insurer insurance company pay the full amount of the estimate to repair my truck.

I was behind this person on a two lane street(,one lane north and one lane south) when he went to the far left side with out signaling and than came back cross the lane without signaling to enter and parking lot.He was in a full size ford pickup truck,iwas in a small nissian pickup.I tried to stop and was blowing my horn but he still hit me.a witness was passing by and witness the hold thing.The police came out got statements from me and the other driver.The witness gave and statement to the fact that i stated.The police did not issue any tickets at the scence.I recieved my incident report and they have the other driver with different violations,the witness statement was attached to the report also.His insurance company contacted me later for a recorded statement,also my witness was contacted.They sent and adjuster out the next day.The claims rep.for the other driver contacted me about a week later and stated the we were equally at fault and that they were only going to pay half.