Last-click attribution gives the entire credit for a sale to the final touch before the lead. It is the default in most dealer reporting because it is simple to compute. It is also the reason a lot of dealership ad budget is spent on the wrong things.
The touch that wins is rarely the touch that worked
A buyer might discover a model through a video, compare trims with an AI assistant, return through a branded search a week later, and only then submit a lead. Last-click hands the whole sale to that branded search. The work that created the demand gets zero credit.
Grade vendors on last-click long enough and you defund everything that builds demand and overfund everything that catches it at the end. The numbers look fine. The budget is quietly wrong.
Full-chain attribution
The fix is to credit the whole chain. Trace revenue from the first anonymous click through the lead and the deal to the service drive that follows, and tie spend to that entire path rather than to its last step.
It also means counting the revenue that arrives after the sale. A customer who services with you for years is worth far more than the deal gross alone. Attribution that stops at the sale misses most of the value a good first touch created.